People put trash in the trash bin. The garbage truck takes the trash away.
The garbage truck makes rounds. It collects a lot of trash at once. One truck can hold 10 tons of trash. The trash is taken to a center.
At the center, the trash is sorted. Machines sort it. People oversee the process. Sorting takes 2-3 hours.
The sorted trash is compressed. Plastics are cleaned. Plastics are turned into small pieces. These pieces are sold onward.
Why do some people think trash is mixed together? The garbage truck has two compartments. One type of trash goes into one compartment, another type into the other. When people don't see this, they think all the trash is mixed together.