Reaction - How the delegates felt about learning experience, and can be through things like post training surveys and verbal feedback
Learning - Measuring how much the delegates increased their knowledge, and can be measured through interviews or tests for example.
Behaviour - The amount of learning that is applied back on the job and is usually measured over time through both interviews and observations
Results - The effect on the business resulting from the training. This is measured through normal management measures, but can often be hard to isolate what changes are from the training and what are from other factors. One needs to consider a control group for comparisons.