University of Texas at Austin: Thomas Dillig's "Principles of Typing"
Read these slides, which will define typing, and explain why we need typing and how types compute. What is the difference between dynamic and static typing? Do you know any language with dynamic typing?
Click http://web.archive.org/web/20160727132645/http://www.cs.utexas.edu/~tdillig/cs345H/lecture9-6up.pdf link to open resource.