They are not necessarily the same thing, although they do cover similar material.
Precalculus is specifically designed so that you can take Calculus after you take Precalculus.
College Algebra isn't necessarily designed this way. Although a college algebra course will probably cover many of the things you need to know to succeed in Calculus, it may not cover certain types of problems which make the transition to Calculus a bit easier.
Depending on the school, College Algebra might not be considered enough preparation to take Calculus--i.e. it might not count as a prerequisite (although it's also possible that it does). Precalculus will certainly be considered adequate preparation for Calculus.
One other possible difference is that Precalculus may cover trigonometry, and College Algebra may not. (This may or may not be true--it varies by school. Check if you aren't sure.)
If both courses are offered, then the one called "College Algebra" is probably easier, and the one called "Precalculus" is probably harder.
If you are offered the choice between both of these courses, then I would recommend College Algebra if you just want to take the easier course, and you are positive that you are never going to take calculus (which means that, in particular, you are positive that you are not going to get a degree in a science). Otherwise I would recommend Precalculus.
If you feel unsure, I would recommend Precalculus, because it leaves you the option of taking Calculus later. I'm probably biased, but I think that Calculus is a very important and beautiful subject.
