how do you save game progress on the ps3?

Question

do you have to buy like a memory card

Answer 1

All of the PS3's have a built in hard drive and a memory card isn't needed.

The PS3 games for the PS3 save automatically. When ever you are playing a PS3 game and the game is saving there might be a little flashing icon on the screen letting you know that the game is saving, or you can just look at the hard drive light indicator. When a game is saving or when there is hard drive activity the hard drive indicator will flash orange.

Answer 2

No, you don't need a memory card, all PS3 versions have a built-in HDD (2.5" - sam as in laptops). PS3 uses an autosave function - you'll see a saving icon when your game is being saved and HDD light (near USBs will flash). However, some games allow you to turn this function off. Unfortuntely, console games with PC saving system (saving when you want to) are rare to find.