The quote function prevents its argument from being evaluated. So the
following expression evaluates to the symbol a, not the value that the
symbol is bound to.

> (quote a)
a

eq? is an equality predicate that allows comparison of things besides
numbers, in this case symbols:

> (eq? (quote a) (car (list (quote a) 2 3)))
#t

The single quote character is syntactic sugar for the application of
the quote function. In all cases, the single quote applies to the
single expression that follows it:

> (eq? '< (cadr '(0 < 1)))
#t
> 

Note that the following three expressions return exactly the same
structure:

> (list '0 '> '0)
(0 > 0)
> (list 0 '> 0)
(0 > 0)
> '(0 > 0)
(0 > 0)
>