For students
Keep what you write
Anything you want back later has to be saved as a project. A project belongs to your account, so it is there from any machine you sign in on.
Saving and finding
Save your work and give it a name you will recognise in a month. My Projects lists everything you have saved, and you can filter by language or search by name once the list gets long.
Some languages let a project hold more than one file, which is what you want as soon as a program outgrows a single page.
Sharing what you made
You can share a project with somebody else, but who you can share it with depends on whether you are on a team.
On your own account
You can only invite people who are on your account, and if you are on your own, that is nobody. To show a friend, set the project so anyone with the link can open it, and send them the link.
Good for showing somebody what you built.
On a teacher's account
The people on that account appear when you search, so you can invite a classmate or your teacher by name.
Good for group work, and asking a teacher to look at something.
What next
When something does not work, and it will not, regularly, there are better things you can do.
Open and manage your projects covers finding, renaming and organising what you save.