for the user

formula

The package definition. A formula provides instructions on how to install packages and their dependencies, such as where to find tar.gzip files for download. You will find them in /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula. An example:

/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/openssl.rb

Keg

A Keg is the installation prefix of a formula, such as:

/usr/local/Cellar/openssl/1.0.2s

cellar

All Kegs are installed into the cellar. It's just the folder where Kegs are put and then Brew adds symlinks for them to the /usr/local folder.

★ ls -l /usr/local/Cellar
★ brew list
★ brew ls

tap

A tap is a Git repository containing extra formulae. Homebrew has the capability to add (and remove) multiple taps to your local installation with brew tap and brew untap. Taps are found in the same location as formulae:

/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core

bottle

A Bottle is a pre-built Keg used for installation instead of building from source. It can be unpacked. Bottles are basically gzipped tarballs and are located here:

★ ls ~/Library/Caches/Homebrew
.
lrwxr-xr-x   1 sconnan  110522448     118 Jun 11 13:52 bash-completion--1.3_3.mojave.bottle.tar.gz -> downloads/a7c2798be568e712a7808e2c1e7ceefe040013c2d5f3c03df234b5f8443bf9b5--bash-completion-1.3_3.mojave.bottle.tar.gz
.
.
lrwxr-xr-x   1 sconnan  110522448     101 Jul  5 15:28 telepresence--0.101.tar.gz -> downloads/0e649255c34e06674517f37c38d0064ce677254a514f46cce76a7c9c0256ca8b--telepresence-0.101.tar.gz
lrwxr-xr-x   1 sconnan  110522448     119 Jun  4 17:32 terraform@0.11--0.11.14.mojave.bottle.tar.gz -> downloads/661f2d14555601dfa48197976a420d0230f34640fbf20fa3c38540fced2e554e--terraform@0.11-0.11.14.mojave.bottle.tar.gz
.
.
lrwxr-xr-x   1 sconnan  110522448     107 Jun 11 11:01 tree--1.8.0.mojave.bottle.tar.gz -> downloads/68ee49d3e261a17eaa26a3732ea07f6b6e7d9f2fb0fa846eb8b72c98a39b8097--tree-1.8.0.mojave.bottle.tar.gz
lrwxr-xr-x   1 sconnan  110522448     110 Jun  4 14:51 wget--1.20.3_1.mojave.bottle.tar.gz -> downloads/a10cbe2e5681852553963cf5cec5c8b6d66614ae9075ec04c3d662671961c413--wget-1.20.3_1.mojave.bottle.tar.gz

cask

An extension of Homebrew which allows you to install native macOS apps with brew. You might find them here:

/Applications/MacDown.app/Contents/SharedSupport/...