How do vaccines create immunological memory?

Immunization is a process designed to help our bodies fight off a particular infection caused by a pathogen in a more effective way, it strengthens the bodies immune response.

Vaccination is the most widely used form of immunization:
considering an example:

A child is vaccinated against a bacteria, and his body is introduced to the antigen (Bacteria 1).

note: antigen refers to any foreign element (in this case Bacteria 1) which enters the body through the outside environment

1. Upon vaccinating the body , Bacteria 1 enters into his body and in response his body produce antibodies which help fight off this bacterial invasion.

2. A very important point to note here is that antibodies are always specific to a particular antigen type.
   So here in this case, antibodies specific to bacteria 1 are produced, let us name them AB-1 (antibody 1)

3. AB-1 fights off all the Bacteria 1 which are infecting his body and now all that is remaining are the antibodies AB - 1

These antibodies have a memory factor and they can now remember the pathogen they just fought against (Bacteria 1), and they circulate his body for years, so next time in future if the child is infected by Bacteria 1, his body will be very quick in recognizing this bacteria and will fight against them