The step-over is one of the moves to beat a defender on offense, deceiving him or her, going one direction and then actually speed up the opposite direction and get quickly behind him or her into the open space.
You would do this by dribbling with one foot.
For example, we choose the outside of the right foot to dribble at the opposite. Once we get to the opponent, we move the foot around the ball to step over, one full loop around the ball, step down to shift body weight and then use the opposite foot, the outside of the opposite foot to actually move into the open space.
To make the step-over effective you have to, of course, really sell the fake move to one side.
You can do this by stepping over, bending the knees so it looks like you actually accelerate into one direction. When you bend the knee, opposite shoulder coming with you so it looks even more like you actually accelerate into that direction.
In the meantime, you adjust the opposite foot using the outside and kick the ball into the open space getting 2 or 3 yards in front of the defender.
If you want to do the more advanced version, you can do the double step-over or the scissors where you actually do the same move with both legs, one after the other.
You step around with the right foot, take the ball quickly with the left foot, step around with the left foot and then accelerate into the open space with the right foot.
That's the double step-over, the more advanced version of the scissor, the simple step-over and it helps you to beat the defender in any way possible.