When you first go to the website. The UI and the terminology might be a bit much. So, let's walk through a few elements.
Glitch makes it simple to get into code right away. They come with three default templates so your configuration is minimal.
Another great thing about Glitch is that it is very easy to find other projects for remixing.
There is a section of Picks from the community as well as some boilerplate https://glitch.com/building-blocks projects that you can easily use to kick-start a project.
Glitch uses the "remix" as a way to make your own copy of an existing project and start a copy just for you.
Inside the editor screen of a project you get a few options
Glitch allows some integrations with Github you can export your project to Github as well as import something from a repository. You can also download the project as well.
Glitch allows you to set up a custom domain for projects now as well. But, I haven't used this feature set just yet.
Each project also has a git repo attached it. You have read/write access to it as well. This is also a feature I haven't played with yet but could open up to some interesting things.
Glitch projects sleep after 5 minutes if they are not used, and those running for more than 12 hours are stopped. This is still a place for ideas and prototypes. Glitch does seem like they might offer a premier plan down the line that might remove some of these restrictions.