'Garage' was a largely American phenomenon in the 1960s (presumably they had more garages per capita). It was 'amateur', guitar based and largely commercially unsuccessful though there was a lot of it, in every garage, so to speak.
It was mainly male, but there were also female groups such as the Pleasure Seekers (featuring a young Suzi Quatro) and The Debutantes, both from Detroit and two of the first all female rock bands, as opposed to 'girl groups' who sang but didn't play the instruments.
Check out that guitar sound - more from the garages in coming weeks.