What is Genetic Modification (GM)?

I think a brief summary of Genetic Modification(GM) will help in understanding more about genetically modified crops such as Bt brinjal,cotton etc.
Genes are those factors which determine the traits or characteristics in an organism. Genetic modification is a relatively new technology through which new organisms are created by using genes from other unrelated organisms. what actually is done is, scientists puts characteristics of one organism organism into another,for eg Genes from fish that can survive in extreme cold water was inserted into strawberries to make them frost resistant.
Currently genetic engineering is used to produce 2 types of crops
Herbicide-Tolerant crops:The main use of HT crops is to make weed control easier and it represents majority of GE crops.
Bt crops: These are geneticallly engineered to produce their own pesticide to kill certain insect pests
I hope you all got a general idea regarding GM crops.