"It generates memory"is the answer to this. Passive immunity is the process by which the antibodies are usually transferred from an immunized person to someone who is not immune. This will provide the unimmunized person protection against a toxin or an agent that may cause several issues. There is a difference between passive and active immunity.
Active immunity involves the body building up some antibodies in order to fight the pathogen that needs to be addressed. Passive immunity, as mentioned earlier, would need to get the antibodies from outside sources. This cannot generate memory as this is more targeted towards the immune system.