Please lemme know.
I'm new at this, and I want to know what's what…

A studio is simply a collection of projects. So if you have a lot of platformers, and want to group them together, then you can put them into a studio.

It's also nice to know that you're curious about things. Well, anyway, welcome Slender_Man12345 to Scratch!

Welcomes,

ErnieParke

Adding on, you can also add curators and managers to manage your studio for you. These people have to be (New) Scratchers, preferably those whom you trust.

Learn more about it here.

Hello Slender_Man12345 and welcome to Scratch and the community

You can read more in the wiki article at http://wiki.scratch.mit.edu/wiki/Studio

I am also new and haven't got a clue. Is it basically a collection of projects? But how do you add them?EEK!!!

You add them by clicking on the button at the top that says “Add projects.”