Pacman is the package manager of Arch Linux and its derivatives.
It uses a slightly more complex syntax than the likes of Yum or Apt given that it doesn’t use word based commands, instead opting for flags.
pacman -S packagename will synchronise a package from the repository. If it’s not installed, it will install it.
pacman -Ss packagename will search the repository for a package that matches the search term.
pacman -Qs packagename will check locally to see if a package is installed.
pacman -Syy packagename will update the repository and install/update the desired package.
pacman -Syyuu will update the system and all installed packages to the latest version.
pacman -Qdt will find all orphaned packages that are no longer required by the system.
pacman -Ru packagename will remove an installed package.