An antibody is a blood protein created to fight against any pathogens which have entered your body. A pathogen can be a bacteria, fungi and a virus, as a result they can cause a disease or an infection.
After two vaccine doses most adults will develop protective antibodies against the Chicken-Pox virus, the vaccination is secure. People who were vaccinated against Chicken-Pox may sometimes develop the disease but it is usually not that severe, with about 50 or fewer red bumps that rarely grow into blisters.
The way it works is a vaccine is created so that our white blood cells are trained to be able to produce many antibodies for the antigens in the case of infection. We use a little part of the disease included in the vaccine so that our defence system reacts and is able to memerise how to create the antibodies. As a result you would be immune from this particular disease. But of course if the disease mutates or changes then we would require a new vaccination as our white blood cells would require a different set of antibodies to kill the antigens. Another method is that perhaps the white blood cell could ingest the bacterium.