Miscellany is like a big bag of things that don't really go together. It's like when you clean your room and you find all sorts of things that you forgot you had, like toys and clothes and books and papers. But instead of just throwing them all away or putting them in their proper places, you decide to keep them all together in one bag, even though they don't really have much in common.
So, a miscellany is a collection of things that are different from each other but are still kept together for some reason. It could be a book of different stories or articles, or a box of random objects that don't fit into any one category. It's like having a bunch of puzzle pieces that don't fit together to make a complete picture, but you still like them all and want to keep them around.