A relay is just an electrically activated switch. For the headlight solution mentioned above the power going to your headlights will run thorough a large gauge wire (10-14 GA) that will run from your battery (or alternator) to the relay and to the headlights. Because this wire is bigger and shorter (shorter because it doesn't run from the battery to the headlight switch to the headlights, just to the headlights) there is less voltage drop. A little voltage drop has a huge effect on your 6 volt bulb brightness and the bigger/ shorter wire greatly reduces that voltage drop and makes your lights brighter. The headlight switch uses a 16 or 18 GA wire (smaller stock wire size) and switches the relay on and off which starts and stops the power to the headlights. The relays you want are sold at about any auto parts store or online for a couple of $ each. Here is a diagram showing how to wire it.
Wiring diagram for headlight relays I've also attached the image. In the image the numbers 30, 85, 86 etc. are the pin numbers on the relays.
A second advantage is you are not running a lot of current through your headlight switch and associated wiring. The headlight switch only uses a little current to switch the relay and the big current load to the headlights goes along the big wires from the battery to relay to headlights.
Here's relays for $2.95 that I bought along with some LED gauge lights.
Relays for $3 Google the topic and there are a zillion diagrams, YouTube videos etc. on the subject.
David
