Teleport is a move that takes up a pokemon's energy when used. They can't just infinitely teleport around and they can't teleport to places they've never been before. The distance a pokemon can teleport increases with their overall strength(their level) so a level 5 shouldn't be able to teleport to the other side of the world. Teleportations generally take up more energy with the longer the distance, so while an inch to the side wouldn't be much for say a level 50. Teleports also generally have a cooldown, so pokemon can't just infinitely avoid attacks by teleporting out of the way.

If you have any more questions, do not be afraid to ask!