Session
What is session?
Session collects data together from a test session or a race. Session can be divided over multiple days, but one session can use only one driver, car and track layout. If any of those change, then you need to have another session.
For example if you have separate car for dry and wet and doing a same race with both cars, then you need to have two separate sessions. Or if Friday practice is done on different track layout than race on Saturday, then you need two sessions.
For these cases it’s recommended to create an event on top of the session to link those together and then be able to compare the data.