When something happens enormously, it happens to a very large degree — not a little, not even 'quite a lot'. People use it to make very feel bigger and warmer: enormously popular, enormously expensive, enormously grateful, it helped enormously. It comes from enormous, which first talks about huge size, but as an adverb it has mostly left the tape-measure behind. A room can be enormous; you would not usually call the room itself 'enormously' unless you mean the degree of some quality (enormously bright, enormously noisy). It is a little more formal and a little more dramatic than very or really, though actually friends do say it when they want to sound strongly pleased, not cold and scientific. It does not mean 'too much' the way excessively does, and it is not a complaint by itself; it just means 'a huge amount'.