It's United's secret top tier frequent flyer program. They get their ass kissed for literally everything, even above full-fare revenue passengers. There's no published requirements for it or information about it - here's the closest thing: https://thepointsguy.com/2016/04/top-perks-united-global-ser...
Fun anecdote: a few months ago I booked a Star Alliance ticket and had a United segment ORD-EWR. I was the only (!) non-upgraded revenue first class passenger on the flight according to the gate agent, but boarded the plane 33rd, thanks to "Global Services" passengers (including the ones in coach) getting to board before me. They also got to order food first, so I was left with the leftover food item, and also got their drink orders and other attention lavished on them first, despite the fact that all the other Global Services passengers in F were flying on free upgrades to F instead of paying for it.
Note that "they got to order first" meant that they literally just skipped over me when taking food/drink orders and when I asked what they were doing the FA brusquely said "We'll get to you in a moment SIR!"
"The biggest benefit to Global Services is the excellent service that is given to those with the status. They receive what can only be described as the royal treatment. Below, some examples:[...]
Irritated with a flight attendant or gate agent? Complain about it and he/she will be reprimanded by HR."
So if you are a GS passenger you can literally get people reprimanded by their own HR? Fab.
