What Is an Edsu App?
Edsu apps are like normal online apps, but instead of signing up and logging in, you grant permissions.
The reason is that all of your data is stored in your Edsu account, not scattered across the internet like with regular apps. Because Edsu apps don't have storage of their own, they need to ask your permission to use some of yours. At some point the app will ask you for your username, and then you'll be taken to a page where you can see which permissions it wants and you can grant or decline that request.
After that, the experience should be much the same as you're used to. The benefits of Edsu - increased user freedom and a platform built for open source principles - are things you'll probably only notice later, when you find that you have more say in your digital life.
Where To From Here?
If you'd like to get into the technical details, the "Hello World App" is a good place to start.