The legs are the biggest muscle groups but so many people in the gym forget (or don't want to) workout their legs. The bigger your leg muscles the more testosterone your body will make (as the muscles are so big) so it really is a win-win situation for the rest of your body if you workout your legs.
Working out your legs at home is very hard - unless you have a barbell. With a barbell (and a squat rack) it is easy to get a good leg workout.
The main Leg Exercises
Squats are one of the most important compound exercises. They work out a lot of muscles - but primarily your legs.
An often forgotten exercise but the calf raises are important!
Leg exercises on the machines
Two great machines to work out your legs are the leg extension machines and leg curls. You might be surprised at first how difficult the leg extension is. But work at it and you'll have big leg muscles.
Another machine you will see in many gyms is the leg press machine.
Leg workouts at home
Despite legs often needed heavier weights or machines, there are some great exercises you can do with limited equipment, such as lunges.