Terminal icon in my dock

The Tech that helped earlier may have placed it on your Dock for their convenience and forgot to remove it afterward. The act of downloading anything from the Mac App Store does not launch the Terminal or place it on your Dock.

Have you opened the Terminal recently?

Well, if there is a small dot under it is open and running. If not, try disabling System Settings > Desktop & Dock > "Show recent applications in the Dock".

If you don't want it there, you can drag it onto the desktop where it then indicate "Remove" and then would be removed from the Dock.