Tab — Auto-complete
On your Bash or ZShell prompt while you navigate the file system, hit tab once. It will “type for you” — automatically matching what it thinks you want— until it finds two files with the same name. Then it will go as far as it can completing only up until the letters provide a match that it can distinguish. If such a unique matching file name exists in the file system, it will automatically complete the matching filename for you and put a space.
If, however, it finds matching two or more matching file names like what you’ve typed, it will complete up to the point where it can distinguish between the filename themselves. That is, where they differ reading left-to-right. Then it will beep at you alerting you that it could not autocomplete.
If it can complete your file typing simply by what you entered, it will so so. In case it cannot, you then press tab again (a second time), which brings us to…