From what I understand the term immunisation means that it prevents you from getting the disease whereas vaccination stimulates the immune system to fight the disease. In the case of Covid the latter applies, you can still catch it but the vaccination lessens the effects.
Vaccination is the method of delivery, i.e by injection but tests are being carried out on pills that could be swallowed and "autoinject" in the stomach (gastric autoinjectors).
The covid vaccine does not prevent a vaccinated person catching or indeed passing on covid but it does lessen the effect and symptoms of covid. For instance it will in most cases prevent the need of hospitalisation of an infected person.
Immunisation is a means to make your body think you have been infected by a disease, (often by injecting a dead or weakened microbe into your body (an antigen)) this stimulates your body to produce antibodies which destroy the antigen. If you are infected again your body now has the antibody to fight that infection and can quickly reproduce more of the same antibody to destroy the desease.
Cheers
Guy