It is the ability of the body to defeat the pathogens invading into the body by producing immune responses against these pathogens like viruses, bacteria etc. It helps our body to stay healthy and fight against pathogens.
It is of two types: Innate and Acquired.
Innate immunity is present by birth and it produces immune response as soon as pathogen invade into the body while acquired immunity is pathogen specific and it is gained by the body over time hence it is not present from birth.
Importance:
It is the first line of defense where various responses such as inflammation , specific cellular responses occurs to fight against pathogen.
It protect the body against the pathogen invading into the body.
It sometimes can also lead to autoimmune disorders where the immune cells cannot identify its own body cell.