Decision tree learning (Wikipedia) [mandatory read, but see remark]

The page contains the crux of the lecture. Its title and the fact that the first link on the page points to a completely unrelated kind of decision trees demonstrate why classification tree is a better term than decision tree. [Mandatory reading, with grain of salt; you most certainly don't need to know that "It is also possible for a tree to be sampled using MCMC." :) ]