Difference between subscribers marked as "Real" and the ones that aren't on SMO panels?

Sorry if this isn't the right place to ask but as the title says, what exactly is the difference? I just find it hard to believe they could get thousands of real people to subscribe to a random channel, so are they all just botted and the "Real" ones are falsely advertised and actually just drop less often or am I just being too skeptical?

Its not false advertising, some of these subscribers are from Advertisement website or exchange like Ytmonster , addmefast...
But I think the majority of them are probably from Botnet ( An infected computer) , These bot have a real IP address and unique browser fingerprints,these bot are considered as real by youtube,but they will have 0 interraction with your channel, don't expect them to watch your videos
These kind of subscribers will never be removed by youtube because they are considered as real

Subscribers not marked as real are simply bot with proxies, they can be removed by youtube at anytime...