Although you can choose from many different site templates when you create a SharePoint website, the most popular is the Team Site template. A website created using the Team Site template is designed with a number of useful features for teams. (Hence the template name, Team Site.)
When you first open your new team site, you can do a number of things right out of the gate. You can store your digital documents in the prebuilt Documents app, and you can get up and running with other apps using the fancy Pop-Up app.
As you hover the mouse over each tile in the Pop-Up app, a description pops up. When you click the tile, you can perform the operation described.

The pop-up guidance allows you to
Get organized with tasks, a calendar, a timeline, and a place to store your digital documents
Get social with a number of social networking features
Share your site with others
Synchronize your local documents with the cloud in order to access them from any device
Simply clicking a tile walks you through a particular task. This is a common theme in SharePoint. SharePoint often tries to be helpful and do things for you automatically. That often makes things very simple but can also lead to confusion by making you wonder, “What just happened?”
In order to get familiar with SharePoint, it’s a good practice to understand what SharePoint is doing for you. When you know what it is doing, it’s very easy to take the next step and extend default behavior to meet your specific needs.