What is the name and salary of that instructor?
Select name, salary from instructor where dept_name  =  'Physics' and salary <  ( SELECT avg ( salary )  FROM instructor WHERE  dept_name   =   'Physics' ) 
name and salary refers to SELECT name, salary; instructor in a specific department refers to WHERE dept_name = 'Physics'; salary less than the average salary in the department refers to salary < (SELECT AVG(salary) FROM instructor WHERE dept_name = 'Physics');