Simplify the following text for a Grade 4 native English-speaking person.
Original: As the world 's second largest manufacturer of pickup trucks , aided by punitive excise taxes on passenger cars , pickup trucks have long been extremely popular in Thailand : between 1987 and 1996 , 58 percent of all cars sold in the country were pickup trucks .
Simplified: Pickup trucks have different shapes , sizes , and uses . Sometimes people would go ride in the back of the trucks to work .