Are Vajrayana and Tibetan Buddhism the same thing? This is a hugely amateurish question, for which I apologize, but: are Vajrayana and Tibetan Buddhism the same thing? If not, how are they related? 

In particular, does the term "Tibetan Buddhism" refer to a specific school of Buddhist thought and practice, or does it just generically refer to any sort of Buddhism that is practiced in Tibet? 

Wikipedia treats the two as separate entities, but some other sources (e.g. this) treat them as effectively the same.
No they are not the same, Tibetan Buddhism is a broader concept that subsumes Tibetan Vajrayana. Also, there's non-Tibetan Vajrayana, some still practiced in e.g. Japan. 

To some degree all schools of Tibetan Buddhism, and particularly Karma Kagyu, recognize three yanas (Hinayana, Mahayana and Vajrayana) as subsequent stages on an individual's path to complete enlightenment. These days many teachers tend to have their student jump straight into tantra right after Ngondro (preliminary stage of Vajrayana training), but traditionally, the student is supposed to master the foundational theory, discipline, and meditation of Hinayana before proceeding to Mahayana, then master Mahayana's practice of subverting one's ego, and attain realization of nonconceptual emptiness, and only then proceed to tantric practices of working with Yidams (generation/completion), the Vajrayana proper.