In Euro Truck Simulator 2 there are several ranks to advance through. You can check out your current rank by going in the Progress History page. The first rank of the game is 'Newbie' and it can be obtained right at the beginning of the game while having level 0.
Enthusiast - Is the second rank of the game which comes right after the Newbie rank. You can get this rank once you've reached level 5.
Skilled Worked - Comes right after the Enthusiast rank and you can get it between level 10-15.
Professional - You can get this rank between level 15-20.
Master - Is the 5th rank of the game and it will be the last rank to unlock all the trucks. You can get it between level 20 - 25.
Instructor - Is the 6th rank, it can be unlocked between level 25 - 30.