The import statement is a way of telling the compiler where to look for class definitions when the class is in a package. It saves you from having to code the full package name when you use a class.
Without the import java.util.Scanner; statement, you would have to code
java.util.Scanner in = new java.util.Scanner(System.in);
For this case maybe it doesn't save much, but if you use the Scanner class many times it can save a lot of typing and make the code a little less cluttered looking.
Note: The class name is Scanner not scanner. Case is important