Overview
Every user can use limited commands to search through the software library of the Ubuntu repository.
Check to see if the program is already installed on the computer
$ apt list --installed | grep -i XXXXX
Where XXXXX is the name or partial name of a program.
Search through the repository to locate a program
$ apt-cache search XXXXXX
Where XXXXX is a keyword in the description of the package or in the name of the package.