What does the Swarmkeeper mean by “horizontal”?

The Ranger Swarmkeeper Gathered Swarm has 2 ability’s that can force horizontal movement. But how do they work?

The attack’s target must succeed on a Strength saving throw against your spell save DC or be moved by the swarm up to 15 feet horizontally in a direction of your choice

Is this horizontal from the direction I am facing, and if so what is stoping me from turning myself to aim freely, or is it horizontal from where the monster is facing? And second we have…

You are moved by the swarm 5 feet horizontally in a direction of your choice.

What’s stopping me again from changing my direction to move freely here too?