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.
Vajrayana was practiced in China, Vietnam and Korea. This is often called esoteric Buddhism.
Kukyo brought esoteric Buddhist to Japan and founded the Shingon sect.
In Russia (well, Kalmykia and Buryatia now) Buddhism was essentially Mongolian Buddhism, which in turn came from Tibet.
And in the US, we have modern formulations of Vajrayana like Shambhala.
I think it would be more accurate to say that these are all forms of Vajrayana rather than forms of Tibetan Buddhism. However, Tibetan Buddhism certain has the most mindshare, the most widespread institutional bases (monestaries and centers established all over the place), so Tibetan Buddhism is the elephant in the room when it comes Vajrayana.
Tibetan Buddhism is not all there is to esoteric Buddhism. There is also Shingon, which I know almost nothing of, except that it exists in Japan. Here is a wikipedia article, which I quote from and added some bold to
Today, there are very few books on Shingon in the West and until the 1940s, not a single book on Shingon had ever been published anywhere in the world, not even in Japan. Since this lineage was brought over to Japan from Tang China over 1100 years ago, its doctrines have always been closely guarded secrets, passed down orally through an initiatic chain and never written down. Throughout the centuries, except for the initiated, most of the Japanese common folk knew little of its secretive doctrines and of the monks of this "Mantra School" except that besides performing the usual priestly duties of prayers, blessings and funeral rites for the public, they practiced only Mikkyō "secret teachings", in stark contrast to all other Buddhist schools, and were called upon to perform mystical rituals that were supposedly able to summon rain, improve harvests, exorcise demons, avert natural disasters, heal the sick and protect the state. The most powerful ones were thought to be able to render entire armies useless.
Even though Tendai also incorporates esoteric teachings in its doctrines, it is still essentially an exoteric Mahayana school. Some exoteric texts are venerated and studied in Shingon as they are the foundation of Mahayana philosophy but the core teachings and texts of Shingon are purely esoteric. From the lack of written material, inaccessibility of its teachings to non-initiates, language barriers and the difficulty of finding qualified teachers outside Japan, Shingon is in all likelihood the most secretive and least understood school of Buddhism in the world.
