Footwork describes the part of the foot that contacts the floor on each step (i.e. toe, ball, heel, or flat). Proper body action causes the correct footwork. The foot itself is not manipulated to cause a specific part of the foot to contact the floor.
For example: If I said, "Take a toe step". The normal response is to think of placing your toe on the floor. Instead think of moving your body in such a way that your toe hits the floor first. So if I said, "Sneak up on someone". Your reaction would be to slowly walk by lifting your knees and sliding your toes on the floor. You are actually taking a toe step by moving your body not by placing your toes using your foot and ankle.
When dancing Smooth, I actually have three heel steps. They are: straight heel, inside edge heel, and outside edge heel. When the gentlemen is in "closed" dance position and takes a forward heel step, it will be a straight heel. If he is in "promenade" dance position and takes a forward left foot heel step, it will result in an inside edge heel step. A "promenade" forward heel step with the right foot would result in an outside edge heel step. As you can see the position of the body determines the type of heel step. Do not try to take a specific type of heel step by manipulating your foot and ankle, let your body position do it.
Your feet do not leave the floor while dancing. There is always some part of your foot on the floor. For example: If I take a forward Smooth step (heel step), your foot goes from flat to heel to flat to ball to toe to ball to flat. When I take a forward Latin step (toe step), your foot goes from flat to toe to ball to flat. It is very important that you use muscle control to change from toe to ball to flat and it doesn't just "clump" down from toe to flat.
There is always some weight on each foot. About 98% of your weight is on your supporting foot and the remaining 2% on the free foot. Even when it is moving the free foot has weight on it. The free foot gives stability just like an outrigger gives stability to a Hawaiian canoe. When you have just a little weight on your free foot, your upper body is balanced slightly different, just enough to give you better balance and control.
Understand what your footwork should be for each body position and movement, then when practicing check your footwork to make sure your body position is correct. The body position creates the footwork not the other way around.