Original: In the United Kingdom and Australia, "timber" is a term also used for sawn wood products (that is, boards), whereas generally in the United States and Canada, the product of timber cut into boards is referred to as lumber.
Simplified: In the U.K. and Australia, "timber" is a term also used for sawn wood products (that is, boards), whereas generally in the United States and Canada, the product of timber cut into boards is referred to as lumber.