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.