A trailer contains good that need to be delivered to its destination as soon as possible. In some cases, it is something that could expire anytime soon, it needs to be delivered as soon as possible or it will get spoiled. Actually, even those goods that don't get spoiled should be delivered as soon as possible because the market demands these products and it will run out of such goods if the new supplies are not delivered immediately. That is where the truck driver came in as he is the one responsible for delivering the goods to its destination in time. They know that the client won't hire him again if he can't deliver the goods on time.
The idea in this game get to the trailer and deliver the trailer to its destination. Each trailer has its goods and you don't need to know what it is. That is not your concern as you just need to focus on the task at hand. You need to attach the truck to the trailer and that will end the level. Next task will be to deliver the trailer to its destination. You will find that this game works like a continued effort as the next level will start from the parking area, where you park the truck.