What is the difference between vaccines and immunisation?

Immunisation is the process of becoming "immune" to a pathogen, in other words once you are exposed to the pathogen again you won't become ill (present with the symptoms). After your body is exposed to a pathogen for the first time, your white blood cells will remember the speific antigen associated with them and when the pathogen comes into your body again, the white blood cells will reproduce rapidly to destroy it quickly before you get ill. For example, if you had chicken pox as a kid you will now be immune to it and unable to get the iconic red spots all over your body. Vaccines are used to make people immune to specific infections. By injecting someone with a harmless or weakened version of a pathogen, you simulate it entering the body for the first time, hence causing you to become immune, as explained above. If you live in the UK you will probably have had the MRR vaccine, making you immune to measles, mumps and rubella.