4.10 Quoting: quote and '
The quote form produces a constant:
The datum can be a symbol, a boolean, a number, a (character or byte) string, a character, a keyword, an empty list, a pair (or list) containing more such values, a vector containing more such values, a hash table containing more such values, or a box containing another such value.
As the last example above shows, the datum does not have to match the normalized printed form of a value. A datum cannot be a printed representation that starts with #<, so it cannot be #<void>, #<undefined>, or a procedure.
The quote form is rarely used for a datum that is a boolean, number, or string by itself, since the printed forms of those values can already be used as constants. The quote form is more typically used for symbols and lists, which have other meanings (identifiers, function calls, etc.) when not quoted.
is a shorthand for