@joebiden track (see fixed geared) bikes have one gear with no freewheel. Basically, the bike can be peddled both forward and backward, and the pedals won't stop spinning until the bike is not in motion. (no ability to coast)
So, a track stand is how track bikes are usually started in a race, from a standing position, like the guy in the red shirt and shoes on the left. You can apply pressure on the pedals both forward and backward, leveraging your weight to balance the bike.
Hope that helps