The word fast, as applied to moves in go, has several meanings. In general a fast move has more than one purpose or meaning. For example a fast defensive move might strengthen your own group while threatening an invasion of your opponent's territory. A fast running move may advance your group farther into the center or offer more subsequent options. The opposite of a fast move is a slow move. Fast moves may be thin and/or light. Slow moves may be thick and/or heavy.
Go books often talk about 'pace', in relation to players who get quickly around the board. It may seem obvious as a plan to do this, based only on a little experience of the game. Orthodox play at pro level developed in Japan in the Edo period along lines that made it less frantic, and more in touch with honte. In fact honte became more-or-less synonymous with 'professional move'. The value of honte may only become apparent in the endgame.
Therefore pacy play can't simply be greedy go, to be good. One gets the impression that those who have played rapidly-developing go and also been top players are important figures in extending the range of strategy.
Examples include Shusaku and Go Seigen; and more recently the young Rin Kaiho, and Kobayashi Koichi. Cho Hun-hyeon has developed a fast style based on 'speed haengma'. AIseems to put even more value on fast development, i.e. switching to different areas of the board sooner and leaving positions behind undefended more often
Certain openings such as nirensei are known for fast developing moves.
Circumstances calling for fast moves