They are different methods of accomplishing the same thing. The point of these containers is to give developers a platform that they can create their apps for that will theoretically run on all Linux distro without having to develop different versions for each distro. Snaps were created by canonical and flatpaks by red hat. Snaps can be used for both desktop applications and server applications while flatpak is focused on desktop only. Snaps will automatically update when the application first starts leading to a slow startup time but also guaranteeing that it is up to date. Flatpak is a bit more popular and is completely open source while snap has a proprietary backend that is controlled by canonical but the core project is open source. Flatpak is designed from the ground up to be decentralized in it’s distribution. You can download a file from flathub.org that will install a flatpak for you but snaps work differently. You need to use terminal commands to install snaps.

There are several other differences but those are the most relevant. So to answer your question, yes… and no.