Yes the infield is the diamond. The middle infield positions (second base and shortstop) tend to be very athletic because they have to have very quick feet and great reaction time. The guys in the outfield tend to be the fastest guys on the team because they have to cover the most ground. The first baseman usually is along with the catcher as the slower more plodding guys but tend to have a big power bat. The first baseman doesn't really have to move around much.

The difference in the gloves is kind of minute in a way. The catcher glove is obviously different. The first basemen glove is real long and wide so that they can easier pick badly thrown balls from infielders. The other positions in the infield have a smaller glove where the pocket isn't as deep. This is so that when they have to make a quick exchange from glove to barehand they don't have the ball getting stuck in the pocket. Outfielders gloves are similar but a bit longer and deeper pocket but not to the extent of a first baseman glove. Pitchers glove can be an infield or outfield glove it just means that the webbing is completely closed, so hitters can't see the grip on a ball.