Controlling a Mount

You can control a mount only if it has been trained to accept a rider. Domesticated horses, mules, and similar creatures have such training.
The Initiative of a controlled mount changes to match yours when you mount it. It moves on your turn as you direct it, and it has only three action options during that turn: Dash, Disengage, and Dodge. A controlled mount can move and act even on the turn that you mount it.
In contrast, an independent mount-one that lets you ride but ignores your control-retains its place in the Initiative order and moves and acts as it likes.