Okay kiddo, so "ities" is actually a suffix - that means it's a little word that we can add to the end of another word to change its meaning.
For example, if we add "-ity" to the end of the word "equal", we get "equality". The "-ity" suffix turns the word into a noun and gives it the meaning of being fair and just for everyone.
Another example is if we add "-ity" to the end of the word "quality", we get "quality". This suffix turns the word into a noun and gives it the meaning of having a high standard or being really good.
So basically, "-ity" is just a little suffix that helps us understand the meaning of different words. It takes a regular word and turns it into a noun with a special meaning.