Aside from live performance, recorded films of theatre and performance are possibly the most informative sources for becoming familiar with various dance styles and aesthetics. Remember that these are usually highly edited and produced and may not be representative of what happened on stage.
These library subscription and free databases allow access and information about all kinds of recorded performances. The four subscription services, Digital Theatre+, Academic Video Online, Royal Shakespeare Company, and the National Theatre Collection have many videos that you cannot find for free online.
There are many DVDs of theatrical performance at Campbell Library in both the general DVD section on the first floor, and in the DVD section of the Performing Arts Collection, on the second floor. Make sure to check Library Search to see which location it is in. You can browse DVDs of theatrical performances under the call number PN.