Let’s assume you are constructing a new house, and you have a contract with a builder. After thoughtful examination of the area, height, and materials needed, he estimates it will take 120 days to build a new home. After constructing the home, it actually took 200 days to built it.
There is a difference between his estimation and the actual result. This applies to query execution plans in SQL server as well, specifically Estimated vs. Actual execution plans.
This tutorial contains an Estimated execution plan as well as an Actual execution plan in SQL Server.

























