A track is a combination of several courses. This can be useful when for example you have a new employee that needs to be onboarded and this person needs to follow several courses that capture everything he/she needs to now (company values, policy, strategy,..). In this way, you can enrol this person in a track, instead of several separate courses.
When you click on Studio and hit Tracks, you will see an overview of all the tracks that have already been made (or none if you have yet to create your first one). If you hit the top right button 'New track', you can give your track a name (e.g. 'Sales onboarding track') and give a short description of the track. The track is now created and you can now add courses to the track. Similar as in creating a course, you can edit the basic track information.