Estimated VS Actual Plan
SQL Server Management Studio gives us the option to obtain both an estimated (Ctrl+L) and an actual query plan (Ctrl+M).
SQL Server will create the plan before executing the statement and it will take some run time decisions.
The actual plan is much more informative and it has information about actual numbers of rows, actual numbers of executions, DOP, memory grants.
The Estimation plan gives the over all view of the cost effectiveness of the query. It is more over like a summarized details vs detail information.