Cons, car, cdr and cadr are list primitives. In Scheme, data objects are combined with the list structure. Primitives are used to access certain elements in lists.
We reference the Structure and Interpretation of Computer Programs. These terms have expanded meanings—so "cons" means "construct."
As noted, the primitive procedure cons means "construct." Cons takes two arguments and returns a list constructed from those two arguments.
car = first item cdr = second and all subsequent items in list cadr = second item
Car refers to the "Contents of Address part of Register" on the original Lisp implementation on the IBM 704. Car will return the first element in a list (page 85).
car = contents of
address part of
registerSimilar to the car primitive, cdr refers to the phrase "Contents of Decrement part of Register." On the original hardware, this referred to the second and subsequent items in a list.
This is a nested application of car and cdr. So this would be the "contents of address part of contents of decrement part of register".
In 2022, Scheme is not widely used. But by understanding the primitives cons, car, cdr, and cadr, we can gain insight into how you can use means of combination.