modular exponentiation versus fast exponentiation

can someone please tell me the difference btw modular exponentiation and fast exponentiation or are the two same? An example would be helpful.
Thanks in advance:)

They are very similar.

Fast exponentiation is used to compute a^n in O(\log n)(assuming the number fits in a word)
modular exponentiation is used to compute a^n\pmod M in O(\log n)

The technique used to compute the answer is same in both