applications are installed with flatpak - basically little containers that contain everything a program needs. sort of like docker
so normally if you wanna install something - let's say minecraft. you would also need to install java. the flatpak for minecraft would have java inside of it so it can be run in its own little container and you don't need to install either
I've been using the same distro for at least 4 years now and I haven't ever had any issues. Fedora on a desktop at home. It's very stable. You don't even need to know too much... although obviously knowing your way around the terminal and knowing some basic things about Linux helps