The sudo apt-get update command is a command-line utility in Ubuntu and Debian systems that is used to update the package manager's list of available packages.
The apt-get command is a command-line package manager that is used to install, remove, and manage packages on Ubuntu and Debian systems. The update subcommand is used to update the package manager's list of available packages.
When you run the sudo apt-get update command, it will connect to the package repositories specified in the /etc/apt/sources.list file and download the latest package information. This includes the names, versions, dependencies, and other information about the available packages.
The apt-get update command does not install any packages or update any existing packages on the system. It simply updates the package manager's list of available packages, which is used by other apt-get commands to determine what packages are available for installation or update.
It is generally recommended to run the sudo apt-get update command before using other apt-get commands, such as install or upgrade, to ensure that the package manager has the latest information about available packages.
You can find more information about the apt-get command and its options in the apt-get man page by running man apt-get in a terminal.