What's the difference between a bed cap and a mattress?

1, different styles, the design of the mattress is relatively simple, and it is a complete fabric spread on the bed surface, with various types and colors. But the design of the bed cap is a little more complicated. The bed cap needs to sew the four corners together and put elastic bands around it to make a suitable cover.

2, the size is different, the size of the sheets is enough to cover the entire bed surface, and there is no strict requirement on the size of the mattress. In order to prevent slipping, the bed cap is bigger than the mattress.