what does cake mean when talking about portal?

Question

when referring to portal some people mention cake whats it mean exactly?

Answer 1

It's an in-game joke. GLaDOS continually dangles the offer of a cake in front of you as a reward for completing her test chambers, while an escaped test subject has written 'The cake is a lie' on various walls hidden around the complex. Many computer monitors, and even a module of GLaDOS herself will list/recite fictional cake recipe ingredients as well.

Spoiler: While technically there is a cake at the end of the game, GLaDOS never intends for you to actually receive it, as you are meant to SPOILERdie in an incineratorSPOILER.