apples and oranges. anymore there are three basic types of pitchers on most major-league rosters. this is a generalization, but your starters will often be guys with decent (~92-94 mph) fastballs and three or even four other pitches to mix in there. they're defined by their control and their stamina; they're chessmasters who can figure out and fake out even the best hitters twice or maybe three times over the course of a game. they're expected to go a good seven innings at least; it became very rare to see a starter put up a large number of complete games but it's getting slightly more common of late.
your relievers are guys who may only throw two or three pitches but they'll throw 'em accurately; they may only last an inning or two but they'll be ready to go in mere minutes (starters can take quite a while to warm up). it's not unheard of to have a guy in your team's bullpen whose sole purpose as a left-handed reliever is to warm up and get ready to strike out that one right-handed hitter who's coming up in the top of the seventh. those are often called spot relievers; most short relievers will face three or four batters while a long reliever is someone who (typically) may face six to eight guys (it's very rare for a reliever to have to go more than two innings unless the starter REALLY screws up). they take over for the starter whenever he (for whatever reason) can't go the distance. those guys will usually finish the games their team is losing.
if the starter can't go the distance and the team is winning, that's when the closer comes in. closers usually only throw one inning - the last one - and in what's called a save situation. that's when you enter the game at a time during which your team is winning but by less than three runs, so you face the potential tying run but strike them out or otherwise induce them to record an out (thereby saving the game for your team). closers are all somewhat similar; since they're only expected to pitch one inning and face at most four or five batters, they almost all have ridiculous velocity (97-100 mph) on their fastball and usually just two other pitches which have a lot of movement and/or are significantly slower so as to throw off the batter's timing. it's about as specialized as pitching gets - well, except for the aforementioned single-opposing-batter lefty spot reliever.
anyway, those are your most common types of pitchers and how they're usually utilized. the starter's job is to win the game the relievers either help the team come back from a bad start or help maintain a lead, and the closer finishes everything off. apologies for the novel but I hope that helps.
Last edited by Captain Sammitch; 2013-11-03 1:55 AM.