A tap is Homebrew-speak for a Git repository containing extra formulae.
Homebrew has the capability to add (and remove) multiple taps to your local installation with the
brew tap and
brew untap commands. Type
man brew in your terminal. The main repository at https://github.com/Homebrew/homebrew-core, often called
homebrew/core, is always built-in.
Your taps are Git repositories located at
varenc/ffmpeg: A tap for FFmpeg with additional options, including nonfree additions.
denji/nginx: A tap for NGINX modules, intended for its
nginx-full formula which includes more module options.
InstantClientTap/instantclient: A tap for Oracle Instant Client. The packages need to be downloaded manually.
osx-cross/avr: GNU AVR toolchain (Libc, compilers and other tools for Atmel MCUs, useful for Arduino hackers and AVR programmers).
petere/postgresql: Allows installing multiple PostgreSQL versions in parallel.
titanous/gnuradio: GNU Radio and friends running on macOS.
dunn/emacs: A tap for Emacs packages.
sidaf/pentest: Tools for penetration testing.
osrf/simulation: Tools for robotics simulation.
brewsci/bio: Bioinformatics formulae.
davidchall/hep: High energy physics formulae.
lifepillar/appleii: Formulae for vintage Apple emulation.