Simply put, a cheeseverse is a universe composed almost entirely of cheese, cheese byproducts, curds of cheese, and cheese like substances. Naturally, a verse like that seems absolutely ludicrous, but the multiverse is a vast place, with a good uncountably large number of universes, surely there's room for at least one cheeseverse?
How Cheeseverses are formed
Most cheeses in our universe are created from processing milk curds. The milk is normally cow milk, though the milk can be from goats or sheep. Before the formation of a universe, there are generally no cows so how can cheeseverses be formed if there are no cows?! One way a cheeseverse can be created is artificial creation of a cheeseverse, extrauniversal beings could be able to take the milk from -illions and -illions of cows, process the milk with even more -illions of bacteria and dump it into a random universe. Whether that universe had life or not is not their concern (and it shouldn't be yours either. oh well, least the lifeforms that aren't lactose intolerant won't go hungry).
Of course, there are still cheeseverses that form naturally. Cheeseverses like that have very strange laws of physics, and no cows or bacteria are needed for its formation.
As the name implies, cheeseverses have a extremely high content of cheese. The most cheese-dense subsections of cheeseverses can be 100% cheese, the areas with the least amount of cheese are holes which are almost similar to areas of "empty" space within a normal universe, but all contents inside are composed entirely of cheese.
Only select few cheeseverses can have holes (i.e. Swiss Cheeseverses), and holes vary greatly in size, from being a few nanometers across to being large enough to hold cheese supergalaxy clusters and cheese turtlies. Holes of those proportions can be considered cheeseverses in their own right (the whole structure can be considered a Level I cheesemultiverse then), and they contain cheesegalaxies.
Larger cheese galaxies often have a supermassive black hole in the center. Cheese galaxies always have cheesestars. In some cheeseverses, cheesestars fuse lighter, more delicate cheese elements like cheesy hydrogen into more compact cheeses like cheesy helium or cheesy lithium. Cheesestars can have cheeseplanets orbiting them, some of which have cheesy water and cheesy oxygen, perhaps with a cheesy ozone layer to protect the cheeseplanet from dangerous cheesy ultraviolet radiation. Cheeseplanets with these conditions may be able to support cheesy life.
Artificially created cheeseverses often start off with life, actually. Cheeses are processed using bacteria who convert lactose into lactic acid, so if an ungodly amount cheese is dumped into a universe, the germs camping out in the cheese will be residents. Some bacteria will die in the vacuum of space, some will live inside holes that still have resources for them to use.
Dangers of the Cheeseverses
Cheeseverses are dangerously cheesy, quite literally.
Some cheeseverses can only permit cheese-like substances due to strange physical laws, wandering into one will turn you into cheese.
Of course, not all cheeseverses have to be like that.
Life of a Cheeseverse
Almost all artificially formed Cheeseverses will have a shorter life than a regular universe because they can rot, or are eaten by their creators. A natural cheeseverse, however, will most likely last as long or longer than an average universe because they have cheese physics, cheese gravity, cheese residents, and yes, even...
Where to find Cheeseverses
They can be found in just about any multiverse randomly, if some sort of cheese-crazed species created a synthetic cheesecheeseverse, you can find cheeseverses there
Types of Cheeseverses
There are artificial or natural, and dangerous or safe, so a few different full types or so Artificial cheezeverses that are dangerous CAN be made, but it takes an insane amount of time to make a verse with different physics and laws to your own, so a dangerous artificial cheeseverse has never been made within our local Cetaverse... Y E T