how to plumbing: Why does my water heater make knocking noises?

I just moved into an apartment and it seems whenever I flush the toilet, use the shower, dishwasher, etc, the water heater makes knocking noises while it’s moving water. I don’t think there’s a difference between hot or cold water. I’m pretty sure it makes the noise the entire time. What could be the possible reasons for this happening?

Thanks in advance! I’ll award points to the best answer.