What takes up Storage Space on a phone(Android)?

[Alphonse]

I recently got a samsung galaxy ace about a month ago.

I noticed that the Storage Space MB was at near 116-118
It would always lower and decrease when I would delete something
But now, it's at 124 for some reason, I don't have that many apps, Just facebook, Google Play store and Fruit Ninja(Its a fun game, dont blame me)
And the weird thing is that my MB has been at 116-118 when these were all installed.

It just instantly increased some how.
I have downloaded a GBA app and 2 games, but even after that, I deleted them.
Yet, I still have 124/181MB

My question is:What uses Storage Space and How can I get my Storage Space to lower?
Already have a MicroSD,

And sorry, i got the problem resolved, turns out that updates take space too xD

But anywho, thanks!