If you have Pacheco’s later text: An Introduction to Parallel Programming (Morgan Kaufmann, 2011) read pp. 83-109, else, we can put this together with the following on-line readings.
A User’s Guide to MPI, by Peter Pacheco, pp. 1-17. This is a partial draft of Pacheco’s MPI text Parallel Programming with MPI (Morgan Kaufmann Pub., 1997) and is available free for download. The published textbook expands on and amplifies this material.
MPI: The Complete Reference, by Marc Snir et al. This is a detailed reference. For this lecture, read the section entitled Introduction and Overview.
RS/6000 SP: Practical MPI Programming IBM Red Book. Optional. The relevant parts are Chapter 1 and Chapter 2 §2.1-2.4. Though somewhat dated, this is an excellent source of information about MPI. Note that the code examples are written in Fortran.