A shell is the command interpreter for the operating system. Bash is my favorite shell, but every Linux shell interprets the instructions typed by the person or sysadmin into a form the working system can use. When the outcomes are returned to the shell program, it shows them in the terminal.
Otherwise, you have to open it and use the Rescan button every time you want to verify for outdated software. You can give up looking for updates manually when you have Avira’s Software Updater program put in. With just one click on, it’ll examine your complete laptop for outdated applications and tell you which ones need up to date.