This is a hormonal method of contraception. It refers to a light weight thin material that contains both estrogen and progesterone. They are put on different parts of the body and hormones released through skin which prevent ovulation.
Each patch lasts three weeks and must be replaced for seven days and must be replaced each weeks for three continuous weeks. The fourth week when a person has no patch that is the week when periods should begin.
This is a good method for people who might not be good at remembering to take pills on a daily basis since the patch is changed weekly. Also some people prefer this method because hormones are absorbed through the skin.
The images above show a patch and the places where the patch can be placed resptively.