Distinction: Intermediate goods are purchased for use as inputs (e.g., flour used by a bakery), whereas final goods are ready for consumption or investment (bread bought by a household; an oven bought by a bakery).
Accounting rule: National income/GDP includes only final goods' value, or alternatively sums value added at each stage, to prevent counting the same value multiple times.
Examples: A car sold to a consumer is final; tyres sold to the car company are intermediate, but the tyre sold as a replacement to a household is final.