A container format for programs, similar to Flatpak and Appimage. Snaps were developed by Canonical, and while they’re technically an open standard, the only place to get them is from Canonical themselves, so it’s sort of a walled-garden thing like phone app stores. Snaps tend to be slower than native packages, and Ubuntu installs the snap version of things by default.

Mint is extremely similar to (and based on) Ubuntu, but with snaps gutted out. There are other differences, but that’s the biggest one