Should this question be reopened?
Noooooooo
It's not only basic knowledge for most who use MSSQL.
Which doesn't actually matter all that much.
But primarily!
It is a clear duplicate.
There are so many posts on serverfault / dba about the memory usage of SQL Server, I don't see why it's not just closed as a duplicate.
It would answer the OP's question quite quickly if it was just closed as a duplicate, serve as a pointer to the tremendous amount of answers about SQL Server memory, and push the point please do your own research more than simply closing it does. (not taking into account comments who are generally regarded as non-existent in the long run)