Here is a list of the completion commands defined in the minibuffer when completion is available.
minibuffer-complete).
minibuffer-complete-word).
minibuffer-complete-and-exit).
minibuffer-list-completions).
minibuf-select-highlighted-completion).
<SPC> completes much like <TAB>, but never goes beyond the
next hyphen or space. If you have ‘auto-f’ in the minibuffer and
type <SPC>, it finds that the completion is ‘auto-fill-mode’,
but it stops completing after ‘fill-’. This gives
‘auto-fill-’. Another <SPC> at this point completes all the
way to ‘auto-fill-mode’. <SPC> in the minibuffer when
completion is available runs the command
minibuffer-complete-word.
Here are some commands you can use to choose a completion from a window that displays a list of completions:
mouse-choose-completion).
You normally use this command while point is in the minibuffer; but you
must click in the list of completions, not in the minibuffer itself.
switch-to-completions). This paves the way for using the
commands below. (Selecting that window in the usual ways has the same
effect, but this way is more convenient.)
choose-completion). To
use this command, you must first switch windows to the window that shows
the list of completions.
next-list-mode-item).
previous-list-mode-item).