Our body is constantly exposed to viruses and bacteria, even when we are not aware of it, and some of them could even make us ill. Our immune system is the one fighting these pathogens and protecting our body.
Each group of cells in this immune system has a different role in the defense system of our body. One of the units in this system is a group of cells that know how to generate antibodies, a specific weapon that is compatible to a specific pathogen that assaulted our body and is effective only against it. These antibodies, which are manufactured by the immune system, stick to the intruder and neutralize him. The immune system gets acquainted with this specific intruder and remembers it for a long period of time so that if he comes again it will face him more rapidly and more effectively. Meaning, next time our body and its immune system encounter the pathogen that caused the disease, it will result in a shorter and easier illness, or it might not even cause any symptoms at all.