He's a YouTuber guy with a kind of distinctive voice, does a lot of Let's Play videos. Recently he's branched out into podcasts & stuff. Seems like a decent dude, unless I've missed recent drama.
It's the concept that government spending actually leads to more consumer spending. To calculate the total economic growth of a government spending package, you add in a multiplier (aka a markiplier) to the total expense to get the total economic growth.
The govt spends 1 mil, 500k of that goes to consumers who spend it again, then 250k of that is spent again, etc. The total growth is 2 mil. This kind of logic is used to justify government spending packages.
I don't know for sure, but my first thought was the homemade compass my dad made for me in elementary school when I lost mine. He made it out of a pencil, duct tape, and a pair of needlenose pliers.