AMPL stands for "A Modeling Language for Mathematical Programming" - dude, acronyms are by no way my strong point, but isn't "A Mathematical Programming Language" more likely? - Cam. It is used to describe mathematical programmes.
AMPL is a commerical software package from Bell Laboratories and is also distributed by ILOG along with the mixed-integer linear programme solver CPLEX.
For more details see the main AMPL website:
and there is a good, fairly comprehensive book on AMPL:
AMPL: A Modeling Language for Mathematical Programming
However, you don't need to pay for AMPL right away! There is a limited functionality student version which also provides CPLEX (the mixed-integer linear programme solver from ILOG) and MINOS (the nonlinear programme solver from the Systems Optimization Laboratory at Stanford University). This Student Version will have enough functionality for the - lose "the", should we be saying "all"? - cam many of the problems you will encounter in the case studies on the OpsRes Web.
You can also use AMPL over the web at the AMPL website's - lose "website's" - cam web interface or you can use AMPL as an interface to many diferent optimisation solvers at the NEOS Server for Optimization.