Look at as many plastic items as you can. On each of them there should be a recycling mark like this (numbers are 1-7). it is in the plastic, not part of the label.

If there is no recycling mark, then that type of plastic cannot be recycled.

Separate the items out according to the recycle number

Look at the items. Could you have guessed that items in each group were made of the same kind of plastic without the mark? How easy would it be to sort plastics just by their look?