The feminist theory was never discovered or published. Instead, it was a universal thought process which was referenced in literature for the past hundreds of years. However, many major pieces of literature have emphasized on it and its basis. Women have always been discriminated against and in the history of the Earth, several events have occurred which have sparked an interest in the theory.
In terms of characteristics, the feminist theory is quite simple and can be explained quite easily. Basically, it concerns the way the literature or other aspects of society address the social, psychological, and political abuse and oppression against females.