I use multiple programs in different categories.(Emacs, terminal, Firefox, music player, IRC client, virtual box, ...)
I was curios, if it was better for my old and slow Ubuntu Desktop to use work-spaces instead of minimizing programs and switching to them? I have seen people running dozen Firefox instances each with multiple tab's open but each Firefox instance is on different work-space.
Does using work-spaces, like that, help with using resources or that just need a very powerful peace of hardware?
If I remember correctly, a workspace is just a "container" for programs. Anything running inside a workspace is still active and using processing power, even if it's not the "active" desktop.
Some programs may treat themselves as minimized or hidden when their workspace is not available, but there should be little to no performance gain or loss.
Meaning, there should be little to no difference between running one Firefox process on each of four workspaces versus running four Firefox processes on one workspace. If anything, there will be a (very) slight performance loss because the system needs to keep track of four workspaces.
As to why, programs in a non-active workspace are still active themselves. A download in Firefox on one workspace will still continue if you're in another. A YouTube video playing in one workspace should[citation-needed] be audible from another workspace.