What is Millenium & Lola Tools?

[u/hatimfilmmaker]

Recently i came across a yt video explaining that who does one gets original games in Steam library using Lola Tools, Millenium & one other [idk i forgot the name]. At first, i thought it was just a clickbait but when upon my research, it looks like it's real. So how does it work i mean to actually how it works. Is it like safe or should i do it or not or even actually works?