I have a quibble with the accepted answer here.
-n is an alias for -T root. So including
-n doesn't actually mean that there is "no prefix" as much as it means the command will be bound to the root table, which is "not recommended".
The root table is used for keys pressed without the prefix key:
binding ‘c’ to new-window in the root table (not recommended) means plain ‘c’ will create a new window
What this seems to be saying is that:
bind -n c new-window
Will create a new window when
c is pressed, and indeed, it does.
The dry humor in the author's phrase "not recommended" is the fact that "c" will of course be pressed many times in the average tmux session, given that "c" is the third-most frequent letter in English.
For another example, here is fast tmux window switching (using PageUp/PageDown keys):
bind -n PPage previous-window
bind -n NPage next-window