https://www.youtube.com/watch?v=pLPpl2ISKTg

It's well worth the watch, but tl;dr: it's a long-con scam. They invest as long as it takes to establish a relationship with you, and then engage you to do something (crypto mostly, apparently) involving cash online. They will say they made a bunch of money, and point you at the super-easy online exchange they used. You buy the crypto, you see the crypto increase in value (because it has in the real world) so you buy more, and more and more.

The problems start when you say you want to cash out. They switch from "buy more, it's going up" to "there are fees to withdraw, just deposit another <whatever> and then you'll get the withdrawal amount plus <whatever>" and of course no money ever comes out.

Oliver interviews people who have lost hundreds of thousands of dollars this way, some of whom still believe that if they just toss in another <whatever> it will all be resolved and they'll get their money back. It's very sad, and I'm not doing the video justice.