Definition - What does Three-Tier Client/Server mean?
A three-tier client/server is a type of multi-tier computing architecture in which an entire application is distributed across three different computing layers or tiers. It divides the presentation, application logic and data processing layers across client and server devices.
It is an example of three-tier application architecture.
Techopedia explains Three-Tier Client/Server
A three-tier client/server adds an additional layer/tier to the client/server-based two-tier models. This additional layer is a server tier that acts as an intermediary or middleware appliance. In a typical implementation scenario, the client or first tier holds the application presentation/interface and broadcasts all of its application-specific requests to the middleware tier server. The middleware or second tier calls the application logic server or third tier for application logic. The distribution of the entire application logic across three tiers helps optimize the overall application access and layer/tier level development and management.