In Haskell:

Variables? What state? Everything is puuuuuuuuure.

In Python:

Everything is an object (numbers, true/false values, strings, etc), some are mutable and some are not. Variables are temporary labels on objects (think of them as hard links).

In Rust/C++:

There are various types of boxes / smart pointers (shared, unique, heap, etc), and unsafe / raw pointers should be avoided when possible.

In C:

Not every variable has a data type, e.g. void or function pointers.