I don't understand the difference between a tuberculosis vaccine and the tuberculosis test (the one where they inject something and read it a couple days later). does an actual vaccine exist? can you clarify?

A vaccine is used to prevent a disease. There is no approved in US vaccine for TBC. The test injects a part of the tuberculoisis germ to see if you body had been infected with TB and made antibodies to it. If so it will get raised and red. But must be interpreted by a trained observer. If you have an immune issue however, but have had TB you may get a false negative test.