How does Hidden Power work in Pokemon GO?

Question

I don't get it. Is there a special factor that decides if it gets HP and what type it is? Or is there only a select few that gets it?

Answer 1

Though the move displays as Normal type, it differs from Pokemon to Pokemon. In GO, it doesn't rely on IVs, instead being randomly selected from every type except Normal and Fairy. This means that two otherwise identical Pokemon will probably have different Hidden Power types. In addition, when a Pokemon with Hidden Power evolves, the move's type will be rerolled.

There are other mechanics that go beyond the bare basics; the Bulbapedia GO Hidden Power section is a good place for a brief overview.