This exercise is called the adductor slide. It's a great exercise to strengthen the adductor muscles, as well as helping hip and pelvic stability.
There are slide discs and roller boards available to help perform this exercise. However, to get started on this straight away, without having to purchase anything, all you really need is one foot that can slide smoothly, and another which is planted with some friction to give it stability.
You can perform this at home, perhaps at a point in your house where the carpet meets the floorboards or tiles. Here, I'm using my carpet protector.
1. Lower yourself down into what is effectively a single leg squat, as your opposite leg slides out along the slippery surface.
2. Keep your centre of gravity centred over the stance leg as you drive that hip backwards.
3. Pull back with both inner thigh muscles (your adductors) as you return upright.
Reps: 8 on each side