Why is the difference between an expression and a statement [duplicate]

Answer 1

An expression is a instruction to be executed that returns a value (even if it returns a void).

A statement is used to form the sequence of a program (e.g. if-then, while-do statements). A statement can be simple or complex and can contain 0 or more expression.

As @Frédéric Hamidi said, a ; is a valid statement.

Wiki on:

• Expression
• Statement

Answer 2

Expressions do "return" a value, though they may be cast to (void). Statements don't evaluate to anything and only have side effects.

E.g. ; is a statement by itself, evaluates to nothing, and has no side effects.