Buffer Gate?

Can TWO Inverters in series form the Buffer Gate?
I mean will it(IC 7404) be able to use as buffer gate?

Where exactly is Buffer Gate application?

A buffer is just a non-invering amplifier, the input is the same as the output minus a propagation delay which will be doubled as you're connecting two gate one after another.

A buffer can be used to to drive more inputs from a single gate than would otherwise be allowed.