Not in STEM pls be nice to me.

Are all of these things related by some underlying concept or fundamental idea?

>Gödel's theorems
>Cantor's diagonalization
>Halting problem
>Busy beaver numbers
>ZF Set Theory
>Lambda calculus

Basically I have been reading about them and it seems that they're actually all similar solutions/theories related to the same underlying problem. Is there an abstraction or something that connects them all? What branch do they all fall under?