What is concepts of reliability and validity as they pertain to psychological testing?

Question

I have a test comming up and I am confused by the concepts of reliability and validity as they pertrain to psychological testing. Can someone explain this to me? thank you!

Answer 1

http://fcit.usf.edu/assessment/basic/basicc.html

Answer 2

http://drdavespsychologypage.intuitwebsites.com/Test__Good_Qualities.pdf