pacman is the Arch Linux package manager

Basic commands

pacman -S package_name     # Install package
pacman -Sy                # Update package database only
pacman -Su                # Upgrade installed packages
pacman -Syu               # Update system (sync + upgrade) (both above)

All about managing:

pacman -Ss search_term         # Search for packages
pacman -Si package_name        # Show package info (remote)
pacman -Qi package_name        # Show installed package info
pacman -Ql package_name        # List files installed by package
pacman -Qo /path/to/file       # Find which package owns a file