Boxing Style Terminology

In boxing, no two fighters' styles are identical. A boxer's style is evolved as he applies what he has been taught or picked up in practice, and performs it in such a way as to suit himself. Nonetheless, many terms are used which broadly describe a boxer's style. Note that a boxer is not necessarily limited to being described by one of these terms. A fighter may be at both in-fighting and out-fighting, a good example of this being Bernard Hopkins.

Boxer/Out-fighter

Muhammad Ali
A classic "boxer" (also known as an "out-fighter") seeks to maintain distance between himself and his opponent, fighting with faster, longer range punches, most notably the jab. Since they rely on weaker punches such as the jab, boxers tend to win by points decisions rather than by knockout, although some out-fighters (such as Lennox Lewis) have notable knockout records. These boxers attempt to control the fight by using their jab to keep their opponent at range, and using fast footwork to evade any opponent that closes in. They are often regarded as the best boxing strategists due to their ability to control the pace of the fight and lead their opponent, wearing him down gradually, and exhibiting more skill and finesse than a brawler.
Notable boxers include Muhammad Ali, Sugar Ray Robinson, Sugar Ray Leonard, Roy Jones Jr., Gene Tunney, Lennox Lewis, Larry Holmes, Chris Eubank, and Floyd Mayweather, Jr.

Boxer/Puncher
A boxer-puncher is an out-fighter who is known for having very powerful punches, often with the ability to knock out opponents in a single good shot. They use similar movement tactics of an out-fighter, but instead of winning by decision, they tend to wear their opponents down by using combinations before scoring the knockout and they move to the inside instead of away like out-fighters. For a fighter who uses this style to be effective, they need to be well rounded.
Notable boxers include Joe Louis, Lennox Lewis, Muhammad Ali, Sugar Ray Robinson, Sugar Ray Leonard, Thomas Hearns, Jermain Taylor, Jack Johnson, Naseem Hamed, and Oscar De La Hoya.

Brawler/Slugger
A brawler is a fighter who generally lacks finesse in the ring, but often makes up for it by volume of sheer punching power. Many brawlers tend to lack mobility in the ring and have difficulty pursuing fighters who are fast on their feet. They prefer a more stable stance from which they may throw the harder, slower punches (such as hooks and uppercuts) and tend to ignore combination punching. They may also have a tendency to load up on their punches more (to pull back the arm before throwing the punch so as to have a greater distance to gather momentum over before the punch's impact). Their slowness and predictable punching patterns (single punches with obvious leads) often leaves them open for counter punching. Brawlers generally are able to take substantial amounts of punishment to make up for their vulnerabilities. The object of the brawler is to win with one punch when given the chance.
Notable brawlers include George Foreman, Marvelous Marvin Hagler, Ricardo Mayorga, Rocky Marciano, Nigel Benn, Samuel Peter, Roberto Duran, James Toney, Kelly Pavlik, and Butterbean.

In-fighter (swarmers)
In-fighters or swarmers stay close to an opponent, throwing intense flurries and combinations of hooks and uppercuts. A successful in-fighter often needs a good "chin" because this usually involves being hit with many jabs before they can maneuver inside where they are more effective. A fighter who operates best at close range is generally shorter and has less reach than his opponents and thus is most effective at a distance where the longer arms of his opponents make punching awkward. However, several fighters tall for their division have been relatively adept at in-fighting as well as out-fighting, including Riddick Bowe and Bernard Hopkins. Fluries due to a sheer lack of skill and technique occur when a fighter allows the bout to become emotional. When a fighter is angry, he will often make mistakes and commit to wildly thrown punches in order to end the fight quickly. Many short in-fighters utilize their stature to their advantage, employing a bob-and-weave defense by bending at the waist to slip underneath or to the sides of incoming punches. Unlike blocking, causing an opponent to miss a punch disrupts his balance, permits forward movement past the opponent's extended arm and keeps the hands free to counter. Some in-fighters have been known for being notoriously hard to hit, with examples including Mike Tyson, Joe Frazier and Sonny Liston.
Notable in-fighters include Joe Frazier, Sugar Shane Mosley, Mike Tyson, Jose Luis Castillo, Evander Holyfield, Felix Trinidad, Marco Antonio Barrera, Manny Pacquiao, Max Baer, and Ricky Hatton.

Style matchups
There is a generally accepted rule of thumb about the success each of these boxing styles has against the others. In general, an in-fighter has an advantage over a boxer, a puncher has an advantage over an in-fighter, and a boxer has an advantage over a puncher. Naturally, many other factors, such as the skill level and training of the combatants, determine the outcome of a fight, but the widely held belief in this relationship among the styles is embodied in the cliché amongst boxing fans and writers that "styles make fights".
Punchers tend to overcome swarmers or in-fighters because, in trying to get close to the slugger, the in-fighter will invariably have to walk straight into the guns of the much harder-hitting puncher, so, unless the former has a very good chin and the latter's stamina is poor, the brawler's superior power will carry the day. A famous example of this type of match-up advantage would be George Foreman's knockout victory over Joe Frazier.
Although in-fighters struggle against heavy punchers, they typically enjoy more success against out-fighters or boxers. Out-fighters prefer a slower fight, with some distance between themselves and the opponent. The in-fighter tries to close that gap and unleash furious flurries. On the inside, the out-fighter loses a lot of his combat effectiveness, because he cannot throw the hard punches. The in-fighter is generally successful in this case, due to his intensity in advancing on his opponent and his good agility, which makes him difficult to evade. For example, the swarming Joe Frazier, though easily dominated by the slugger George Foreman, was able to create many more problems for the boxer Muhammad Ali in their three fights than Foreman could. Joe Louis, after retirement, admitted that he hated being crowded, and that a swarmer like Rocky Marciano would have caused him style problems even in his prime.
The boxer or out-fighter tends to be most successful against a brawler, whose slow speed (both hand and foot) and poor technique makes him an easy target to hit for the faster out-fighter. The out-fighter's main concern is to stay alert, as the brawler only needs to land one good punch to finish the fight. If the out-fighter can avoid those power punches, he can often wear the brawler down with fast jabs, tiring him out. If he is successful enough, he may even apply extra pressure in the later rounds in an attempt to achieve a knockout. Most classic boxers, such as Muhammad Ali and Lennox Lewis, enjoyed their best successes against sluggers.