HEllo Bakers!

I wasn't sure of where to post this question, if here in "How Do I?" or if in "Recipes" but here I go!

I'm sorry if I sound stupid asking this type of questions, but I'm still a newbie at baking and I've never went to a baking school. My question is, Which ingredient (in cake recipes) or method (in making cakes) is the one that makes the cake spongy?  Some of my cakes are spongy (not as much I would've liked tho) and some of them are not. So I'm guessing that if I find out what it's that makes cake spongy, I could improve my cakes in that area.

Thank You so Much in Advance !

i seperate the eggs and add the egg york to mixture then whisk the whites and add in at the end this makes them spongy as more air is caught inside