What is the difference between Layer and Tier? [duplicate]

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• What's the difference between “Layers” and “Tiers”? 13 answers

I am confused about these two terms. What do these two terms mean? What is the difference between Layer and Tier?

Answer 1

Sometimes people use them interchangeably but in my mind a layer is a logical separation (GUI, data access, business logic etc)and a tier is a physical separation (separate servers...ie web server, database server etc).

See the entries in Wikipedia: Multitier Architecture vs Multilayered architecture

Answer 2

Tier is often used in reference to 3 tier applications (GUI, business objects/logic, database access), or n-tier applications. Often times in discussing a 3 tier application, someone will use "layer" when referring to one of the tiers, such as the "business layer" or "database access layer". They are often used interchangeably. While there are probably technical definitions of these the differentiate them, I wouldn't get bogged down on it. Often times these terms take on a different flavor in different contexts.

As such I like to further clarify terms when using them in everyday conversation. If I say "service" it could mean "Windows Service", "WCF Service", "Some SOA type of service", or "web Service". So I would never just say "service" because the person I'm talking to might interpret it one way and then we will be on totally different pages.