Sometimes I see articles saying command of brew tap before brew install something. I am wondering what does tap mean? And why must I run tap before install?
Answer
The tap command allows Homebrew to tap into another repository of formulae. Once you've done this you've expanded your options of installable software.
These additional Git repos (inside /usr/local/Homebrew/Library/Taps) describe sets of package formulae that are available for installation.
E.g.
brew tap # list tapped repositories
brew tap <tapname> # add tap
brew untap <tapname> # remove a tap