Vaccines contain weakened or dead pathogens, its toxins or its proteins. It stimulates the immune system so that it can recognise the pathogen and protect an individual from future encounters with the same pathogen.
The vaccine consists of dead and attenuated (harmless) microbes which when exposed to the body, creates a defence attack against the microbe and destroys it. In this process, a memory of this specific microbe is created so that when the same microbe attacks an organism next time, the immunity (strength to fight) is increased and the microbe is killed much more quickly.
Since immunity obtained because of vaccines is due to the direct exposure of the weakend or dead form of antigen, this type of immunity is an example of active immunity. Therefore vaccination is a type of active immunity and not passive immunity.
Also this type of immunity is obtained during one's lifetime. Thus immunity provided by vaccine is acquired in nature.