It's basically doing what "playonlinux" used to do. It separates containers of different Wine setups - so for example you have some old Windows game that only runs in a window at 1024x768, you make one "bottle" to deal with that, but it doesn't mess up the settings for running a separate "bottle" for a more recent a Windows-only utility program, which requires a fullscreen desktop, and dotnet4.5 and directx etc.

It also gives the setup a GUI, and lots of dropdown menus for setup, which is easier for most people.

There's a bit of crossover with Lutris - though Lutris works particularly well for games that are already in its database, but it's sometimes quite difficult to install anything outside of that - I found bottles to be a lot easier for installing fairly obscure or forgotten software - generally old games, obscure games and hardware configuration utilities for A/V equipment, but also sometimes stuff like indie games or other games that aren't on Steam.

I do use Playonlinux, Lutris and Bottles, as for some reason, sometimes I've been able to get a program running in one and not the other. I very rarely install anything on the default "raw" system Wine any more.