Lefty Gloves The confusing thing about left-handed baseball gloves is that they actually go on the player's right hand. Since left-handed players throw with their dominant left hands, they catch with their right hands--hence the need for left-handed baseball gloves that go on right hands.
Catcher's mitts Are called "mitts" because they lack individual fingers, like mittens. They have extra padding and a hinged, claw-like shape

Catcher's mitts

that helps them to catch 90+-mile-per-hour fastballs, and supply a good target for pitchers. If needed to catch a knuckleball, a catcher will generally use an even bigger mitt. Sizes of catcher's mitts, unlike those of other gloves, are measured round the circumference, and they usually have 32- to 34-inch patterns.

First basemen's mitts

First basemen's mitts also lack individual fingers. They are normally longer and wide to help them "pick or scoop" badly thrown balls from infielders. These mitts generally have 12.5- to 12.75-inch patterns, measured from wrist to the tip. Note that, because first basemen are typically left-handed, first basemen's mitts are swiftly available to fit on a right hand. Hank Greenberg, a famously blundering fielder, is frequently credited as first to wear this style of glove in the field.

Infielders  gloves , in contrast to the first baseman's mitt, are smaller. They have shallow pockets to permit fielders to get rid of the ball simply to make a fast throw to a base. Frequently the webbing will be

Infielders gloves

open to permit mud to move thru the glove so the infielder doesn't pull out a few dust when making an attempt to take away the ball from the glove. Infielder's gloves usually have 11- to 12-inch patterns, measured from the wrist to the tip.

Pitchers gloves

Pitchers gloves often have a closed, opaque, webbing to permit pitchers to hide their grip on the ball which, in part, sets the behaviour of the pitch in flight from the batter.

Outfielder's gloves are customarily quite long with deeper pockets, to help with catching fly balls on the run or in a dive, and to keep outfielders from needing to bend over as far to field a ground ball. These gloves generally have 12- to 12.75-inch patterns, measured

Outfielder's gloves

from wrist to the tip. They're often worn-in differently than those of infielders, with a flatter squeeze instead of the infielder's rounded style.

Softball Gloves
Youth Gloves Perhaps the most important point in this section is to avoid the temptation to buy a glove that is to "large" for the person using it with the thought in mind "they will grow into it". What will actually happen is the player will get discouraged and want to quit after the glove falls off his hand a couple of times or you'll get discouraged and either go buy another glove the right size or wonder why "little Johnny" can't keep his glove on like the rest of the guys. Either way its a lose-lose proposition. Buy the right size the first time and avoid needless pain.
Batting Glove