Start Command-line mode. In Command-line mode, you can perform extended commands, which may require arguments.
Recall the previous command line from the history list which matches the current command line.
Recall the next command line from the history list which matches the current command line.
Complete the word in front of the cursor according to the behavior specified in 'wildmode'. If 'wildmode' contains "list" and there are multiple matches then the completion menu window is opened.