Hello, welcome to Linux, here are the apps you installed using Snap. Here are the apps you installed using Flatpak. Here are the apps you installed using apt. Here are the apps you inst- wait, where are you going… what’s wrong? WE WERE JUST GETTING TO KNOW EACH OTHER!!!
@aral welcome to macOS, here are the apps installed using Mac App Store. Here are the apps installed from DMGs. Here are the apps installed from PKGs (try uninstalling those!). Here are the apps installed from Homebrew. Here are the apps...
Like regular software packages they're basically a file structure with metadata, possibly including pre-install and post-install scripts as well.
The main difference is that they're used by a simple installer, not a package manager. So they DO have a "manager" in the form of the installer. It just doesn't keep track of what's already installed, hence good luck removing it.