Difference between Black Mesa and Aperture?

Hey!
Could somebody please tell me what the differnce is between the Black Mesa Research Facility and Aperture Labs in Half Life? Like, is one a'good' side and one 'bad', and does Gordan Freeman support/work for one side? Sorry, I'm not into games and need clueing up!
Also, is there some kind of cake involved with Aperture, if so what is it for?

They are just competing science research labs, and apparently Black Mesa got more government budgeting.

Gordon was a Theoretical Physicist for Black Mesa.

Dem would be correct. Also no , cake has nothing to do with Aperature, it was just a sequence in the game Portal that everyone references, a little joke.

Ahh I see..thanks guys!

I hear Aperture was originally contracted by the US Military for shower curtains.

"I hear Aperture was originally contracted by the US Military for shower curtains."