1. They're used to prove that yes, "My infinity is higher than yours" is a legitimate thing in versus debating
2. Basically it starts on the premise that if you count a matrix of numbers diagonally it will net a larger set of numbers than a horizontal row, which in turn if infinite will mean the diagonal set is a larger set than the horizontal set.
3. The premise is expanded with all real numbers being larger than all natural numbers. Natural numbers: 1,2,3,4,5,6.. you can count all the way to infinity. Uncountable infinity is counting every decimal between 1 and 2, which is impossible. So the set of all real numbers is larger than the set of integers.
4. You can use further manipulations of pure mathematics, abstract algebra, and set theory to create larger sets.
5. Cardinalities are how large a set is.
Aleph-Null is all countably infinite numbers
Aleph-One is equivalent to all real numnbers
Aleph-Two is equivalent to Aleph-One ^ Aleph-One, or Aleph-One ^^ 2
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Aleph Omega is Aleph-One ^ Aleph-One a countably infinite number of times, this would be megaversal+
However you can then have alephs of alephs, like aleph-aleph-one
This goes all the way to Aleph-Fixed Point
Beyond that inacessibles which have their own hierarchy through advanced manipulation of math, this would be omniversal and above