Most of our content is aimed at a specialized audience--undergraduates, grad students, faculty, and professional researchers. Even within that target audience, there can be a wide range of expertise. To help you find appropriate content, we have added a skill level classifications to our resources as follows:

These skill levels are somewhat subjective and should be taken with a grain of salt, but they are intended to help you find content at the right level for a particular purpose. Note that some tools may be marked as "easy" and intended for college freshmen, but they could still be useful to experts. In the case where resources are judged to be not only appropriate for but also appealing to multiple categories, they are marked with multiple levels.