They are both my accounts for different uses. But when I do 'sudo apt install' on one user account it installs the programs on the second.This is outside my normal area ,
you would normally set up multiple accounts [and not share YOUR password with the other user]
the way to set up additional users will depend on your build of Linux and your desktop environment,
so before one of our wizkids in the know jump in to help please state your build [EG. mint/linuxlite/etc] and your desktop [EG . kede, cinnamon , mate/ etc]
It is supposed to do this. When you run a package manager, you are installing things system-wide and this makes your OS stable. It lets applications share libraries, it ensures consistency, and many other wonderful things UNIX brought us. I won't go into the history, but read up on the concepts if you're interested.They are both my accounts for different uses. But when I do 'sudo apt install' on one user account it installs the programs on the second.