Much like you can plug more than one item into the home mains supply, you can power more than one item from a battery or other power source.
At a high level, as long as your PSU is capable of supporting the combined load of RPI and a screen, then you should be fine. You need to make sure that both the RPI and screen operate from the same voltage. If they don't, then you need a regulator or some other converter, or a separate PSU/battery.
You can check the maximum current consumption of the RPI by checking the hardware page for it.
Much like you can plug more than one item into the home mains supply, you can power more than one item from a battery or other power source.
At a high level, as long as your PSU is capable of supporting the combined load of RPI and a screen, then you should be fine. You need to make sure that both the RPI and screen operate from the same voltage. If they don't, then you need a regulator or some other converter, or a separate PSU/battery.
You can check the maximum current consumption of the RPI by checking the hardware page for it.
