noun
member store; participating merchant; franchisee
Refers to a store or business that belongs to a chain, association, or franchise network. The exact nuance (member vs. franchisee) depends on context.
このクーポンは全国の加盟店で使えます。
This coupon can be used at participating stores nationwide.
新しい加盟店がチェーンに加わった。
A new franchise store joined the chain.
チェーン店 is a chain store, which may or may not be a franchise. 加盟店 emphasizes membership in a network.
Compound of 加盟 (かめい, 'affiliation, joining') + 店 (てん, 'store').