Update & Upgrade

Update 
 First, you need to fetch the newest version of Homebrew and all formulae from GitHub using git and perform any necessary migrations. 
 brew update
 
 Upgrade 
 To upgrade all the outdated casks and outdated, unpinned formulae using the same options they were originally installed with. 
 brew upgrade
 
 To upgrade a particular cask or formulae: 
 brew upgrade [installed_formula / installed_cask]