A third$-$tier supplier is a supplier who provides goods or services to a second$-$tier supplier. A second$-$tier supplier is a supplier who provides goods or services to a first$-$tier supplier. A first$-$tier supplier is a supplier who provides goods or services to a company or organization.

A third$-$tier customer is a customer who purchases goods or services from a second$-$tier customer. A second$-$tier customer is a customer who purchases goods or services from a first$-$tier customer. A first$-$tier customer is a customer who purchases goods or services from a company or organization.

A focal firm is a company or organization that is the focus of a study or analysis. The focal firm is usually the largest or most important firm in a particular industry or market.

Examples of third$-$tier suppliers are farmers who sell their products to a food processor, and truck drivers who sell their services to a transportation company.

Examples of third$-$tier customers are retail stores that sell products to consumers, and restaurants that serve meals to customers.

Examples of focal firms are Apple Inc. and Walmart Stores