A time tracking type is a way to categorize your time trackings. It helps you to keep an overview about your different time trackings and to evaluate these later on. Before you can create your first time tracking, you have to add a time tracking type.
You can create a new time tracking type by going to settings / time tracking
Here you will have the opportunity to create a new type by clicking on the "+ Add Type" button. This will open a new pop-up window where you can add your information. First you can enter the name of the type. You can add a short description and choose a small nice icon for that, too.
In the end you just have to save this information. Now you can choose this type, when you are creating a new time tracking.