What does "server", "instance" mean in MSSQLServer 2005

Question

In MS SQLSERVER 2005 I can not understand the following terms

Server

instance

Answer 1

A server is a (physical or virtual) machine running SQL Server software.

An instance is a collection of SQL Server databases that are run by a single SQL Server service, such as an instance. You can view each individual instance that you use in your service console. Each instance can be started or stopped separately.

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Answer 2

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Answer 3

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Answer 4

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