In this lesson on design technology, students are introduced to the concept and use of relays, including identifying their composition and considerations for selecting them. The lesson covers the functionality of relays, explaining how they utilize an electric current instead of manual operation to control circuits and isolate or switch the state of electric current. Key components include the electromagnetic coil and the load circuit, with practical demonstrations on the operation of relays using a 12-volt battery and a push-to-make switch.