So, tier lists.

There's been something of a fad in the last few years of organizing things into tier lists. As far as I can tell it comes from the gaming community, ranking player characters or items or weapons or whatever. The tiers follow the letter grading scale I think most of the English speaking world will have some understanding of; A through F without E with F being a failing grade. Apparently because Japan, an S tier for Superior is added above A.

A fun implementation of this is TierZoo. One of those Youtubers who is also on Nebula, his whole gimmick is he does educational videos (and lifeforms in general) in a very video game discussion style. As if he's a veteran player of an MMORPG called "Outside" in which every organism is a player character. If you want to get a good grip on the tier list phenomenon he provides many examples.