My hot water tank is leaking at the bottom. What causes this? And how do I fix it?

It could be old enough that the base of the tank has rotted, it happens.

Is the water coming from inside where the ?flame plate? Is located?Or perhaps it has begun leaking from the top where the water lines first go into the tank, then just running down the insides?

Either way, I would suggest a replacement.. better to be safe than sorry.

It is leaking from the bottom. No leaking from the sides or top.

Is the heater actually inside the bathroom? Leaking from the jacket of a water heater tells me it can be leaking anywhere, the water stays inside the jacket until it hits the bottom. If this is your case just replace the heater, not worth repairing