Spectating is the act of viewing a match where other people are playing. You can fly freely on the map or follow people
To follow people, currently the keybinds aren't set but to set it you can type this in the console whilst playing
/teambind spectators (yourkey) followprev /teambind spectators (yourkey) follownext
(yourkey) could be a key of your choice, for example PGUP and PGDN for PageUp and PageDown. You can now follow someone. You can change the keys by running the command(s) again.