Terms are the output effects of a statistical model, which may take the form of main effects, nested effects (in a model with nesting), or interaction effects (in a model with cross factors).

Program Terms.exe will list all of the terms and their degrees of freedom for any model that you specify with any number of levels of each of any number of cross-factored or nested categorical or continuous variables.

Doncaster, C. P. & Davey, A. J. H. (2007) Analysis of Variance and Covariance: How to Choose and Construct Models for the Life Sciences. Cambridge: Cambridge University Press.

http://www.southampton.ac.uk/~cpd/anovas/datasets/