OKaaaay...lets see if i really understand this as i ought...flatpack, snap, appimage, etc and all of its ilk are basically designed to enable those using MONO and hence wine and play on linux on there computers so they can have an easy time going outside of safe linux repositories in order to download and use outside programs mainly designed for windows type users who have had it with microsoft windows but still want all of the ease of use of windows but want to have their cake and eat it too on linux and the heck with the security consequences...do i seem to perceive this in an accurate fashion?...DAMIEN
No (and kinda yes)...
They have nothing specifically to do with Mono or WINE or POL, or indeed Windows software.
They are a way of packaging (usually Linux) software that includes ALL the dependencies along with the application, and runs it in an container generally isolated from the rest of the system (which is why they currently don't pick up system themeing).
Upsides are that it makes a single clickable installer that should work on any distro, and that as it contains ALL dependencies it's possible to have different versions of libraries on the same system (where say the application requires an older/newer library as a dependency than the one in the repo).
Downsides are that they'll 'generally' take up more space because of dependency duplication, having all its own dependencies allows for malicious dependencies, and the biggest downsides I see is that they will likely end up being available from all over the web which **IS** a security risk.
So it's not specifically for Mono/WINE/Windows software .. but it can
also lend itself to those because the package can contain its own copies of the Mono libs/WINE/etc.
I'm not saying that all was better before... 
...there are positive things with flatpak, it's the side effects that freak me out
{Hi, my name is
Zac T. Ly}
/
Egg ZacTLy --> 
Not to mention they were supposed to be a universal package to replace the non-competing .deb/.rpm/etc. .. and we've somehow ended up with three of them competing

(and if none wins outright, we'll end up not only with larger packages, but also having to carry two or three times the supporting framework .. and app devs will still have to make a packaging choice)