Beginner question about wetsuits

A wetsuit is a neoprene body suit that comes with or without arms.  It is between 1 and 5 mm thick, depending on where on the suit you measure.  The chest and front of the legs don't need to move that much so those parts are  thicker than other parts of the suit.

People wear them for three primary reasons:

1)  Speed.  You will swim faster in a wetsuit.  The better a swimmer you are, the less of an effect the suit will have on your swim speed, though. 

2)  Buoyancy.  It's darn near impossible to sink in a wetsuit and your legs don't need to do near as much of anything to stay floating so you stay in a better swimming attitude with less energy expended.

3)  Warmth.  Water below 72 degrees gets chilly.  Longer swims might mandate wetsuits so the race doesn't have hypothermia cases to deal with.

You will find that most wetsuits come in three levels of quality and price. The lower end priced suits are pretty basic with the higher end suits using top of the line rubbers and designed better for comfort and durability. Most brands will fit differently on each individual, it is important to get a good fit, this can only be accomplished by trying on several different brands. It is also important to consider the zipper release sytem you feel confident with, nothing worse than not bieng able to get your wetsuit off after a race swim with the sun beaming down on you.