MeWe is an alternative to Facebook and has a focus on privacy. Apparently, part of their reasoning for not letting people preview the site is to protect the privacy of its members (how true that is I couldn't say).
It's only new so there's no surprise that many people have not heard of it before. It was only established in 2016 and hasn't had the publicity that well established social media platforms like facebook have had. It is becoming better known.
Personally, I am 50/50 in regards to MeWe. There's things I like about it but like any business they need to make money to survive and I'm a bit anti- their business model. Their model is the sale of additional features to pay their costs, things like emojis and so on.
Edit: Still, I prefer a company to sell features over selling my private data - which is exactly why I refuse to use facebook.
Here's some reviews to help you decide: -
https://steemit.com/deletefacebook/@...-mewe-reviewed
https://techaeris.com/2018/10/11/goo...-social-media/
https://techaeris.com/2018/10/12/jas...director-mewe/
https://www.macobserver.com/reviews/...ocial-network/
https://venturebeat.com/2018/07/05/i...ewe-thinks-so/