Stand on your right heel with the ball of your right foot, referred hereto after as the "toe", pointed into the air. Your elevated right toe must also start pointed at a 45-degree to the left, or inside. Simultaneously stand on your left toe with your left heel elevated. Do so with your left toe planted comfortably behind your right heel. Feel free to inverse this initial plant if it doing so makes for a more comfortable or natural starting stance. For orientation's sake, you may rather start with an elevated left toe and right heel.
Keeping your back toe and front heel planted, rotate the front heel from 45 degrees inside to 45 degrees outside. This step creates both the allure and primary visual effect of the heel & toe dance.
After heel rotation, bring your front foot back. Plant it toe-down behind your original back foot. Your original back foot has now become your front foot, from which you will execute another heel rotation. You may take a quick additional step to adjust your new front foot if desired. Lift the toe on your new front foot and point it 45 degrees inside. You are now set in a new plant stance with the opposite feet and are ready for a new heel rotation.
Once started, repeat the heel rotation, drop back and switch in accordance with the music's rhythm as often as desired.
Repeatedly placing one foot behind the other will cause you to gradually move backward. There is nothing wrong with this stylistically and if you have adequate dance floor space to do so. However, incorporating a slight hop step into the drop back and switch adds an additional visual effect and allows you to move directionally or perform your heel & toe in one place.
The heel & toe itself can be your entire dance routine, but it may also just be the basis of a more complex routine. Have fun and be creative on the dance floor. Incorporate heel & toe into other steps and add your own creative flair to the motions as desired.