Here is a list of the completion commands defined in the minibuffer when completion is allowed.
minibuffer-complete-word). This command is not available for arguments that often include spaces, such as file names.
minibuffer-complete-and-exit). See Completion Exit.
minibuffer-complete) is the most fundamental
completion command. It searches for all possible completions that
match the existing minibuffer text, and attempts to complete as much
as it can. See Completion Styles, for how completion alternatives
minibuffer-complete-word) completes like
<TAB>, but only up to 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 only inserts ‘ill-’,
giving ‘auto-fill-’. Another <SPC> at this point completes
all the way to ‘auto-fill-mode’.
If <TAB> or <SPC> is unable to complete, it displays a list
of matching completion alternatives (if there are any) in another
window. You can display the same list with ?
minibuffer-completion-help). The following commands can be
used with the completion list:
switch-to-completions). This paves the way for using the commands below. <PageUp> or <prior> does the same. You can also select the window in other ways (see Windows).