If a computer uses 16 bits to specify an address in RAM, then the number of addresses will be

With 16 bits an address can take 2 to the power 16 values, which is 65,536 or 64K.

Writing it as 2 to the power 16 is the exponent form of the same count.

Writing it as 65,536 is that power worked out.

Writing it as 64K is the same number, since one K here means 1024.

All three expressions name one identical quantity.

Add-on: each extra address bit doubles the number of locations that can be named.