5 Lexical conventions [lex]

5.6 Tokens [lex.token]

There are five kinds of tokens: identifiers, keywords, literals,15 operators, and other separators.
Blanks, horizontal and vertical tabs, newlines, formfeeds, and comments (collectively, “whitespace”), as described below, are ignored except as they serve to separate tokens.
[Note 1:
Some whitespace is required to separate otherwise adjacent identifiers, keywords, numeric literals, and alternative tokens containing alphabetic characters.
— end note]
Literals include strings and character and numeric literals.