Flatpaks

Where system packages are distro dependent, Flatpaks are one of several universal package formats. With the other major player being AppImages

Flatpaks receive lots of hate but much of this is unwarranted. In reality Flatpaks do have some enticing benefits. They work on EVERY DISTRO, they are containerized (meaning they don't interact with your system which is great for security and prevents dependency breaks), and they offer the same performance as native system packages. They also often get updates faster than any other packages with the exception of system packages and on distros like Debian actually outpace system package development. They're also built into most DE's app stores which means that they're easy to install as they essentially function as the equivalent to the Mac app store or a better version of the Windows app store.

Where Flatpaks begin to receive some very earned criticism is in their shortcomings which be massive issues depending on your needs.

For instance, if you use Visual Studio/VS Code/VSCodium then you're almost certainly going to use extensions. But because of the way that Flatpak handles system access and permissions this is actually much more work than it would be on a system package. It also means that for instance, when you're using Steam you'll need to use a tool to change what version of proton you use as opposed to simply installing the proton version alongside Steam and enabling it. This doesn't amount to much but depending on how extensively you need an app to have control it's something to consider. They also take more space because each package is isolated and requires it's own copies of dependencies. On a system with few packages this means nothing but if you manage a lot of installations you need to keep an eye on storage.

That being said, they're universal, they're fast, and they offer lots of options and there's even third-party Flatpaks. Making them a great add-on.