If you're wondering how many devices you can use with your brush, the answer is: it depends.
There are two types of toothbrushes: manual and electronic. Manual brushes can be used with any number of devices, as long as they're compatible (i.e. the same size and shape). Electronic brushes, on the other hand, usually come with a specific charger that's meant to be used with that one brush only.
So, if you have a manual brush, feel free to use it with as many devices as you like. If you have an electronic brush, check to see if it came with a charging base or docking station - if so, that's the only device it should be used with.