So according to Wikipedia, genetic engineering involves the isolation, manipulation and reintroduction of DNA into cells or model organisms, usually to express a protein to reach desired effects. The aim is to introduce new characteristics or attributes physiologically or physically, such as making a crop resistant to a herbicide, introducing a novel trait, enhancing existing ones, or producing a new protein or enzyme. So basically it is a genetic trick to make plants or animals or even umans adapt to the needs we have. It is say a way of tricking mother nature. What happens in it is that there is a set of technologies which is being used for changing the genetic makeup of cells and moving the genes across species boundaries to produce novel organisms. It is a very hard task and it involves genetic material and other biologically important chemicals.
This could happen in nature. A brown dog is bred with a white dog and you may get a puppy who has a totally different colour. But the colour range is limited and the odds are it resembles brown and white. For getting a purple puppy you have to breed toward one only if the necessary purple genes were available somewhere in a dog or at least a near relative to dogs. Ideally (though this is not the case so far), a genetic scientist has no such problems. He can take the gene which makes purple from a sea urchin or just a purple flower and use it and he could insert it and achieve the needed colour. But purple puppies fun as they may be are not of any real use and so there are other, more serious uses for genetic engineering.
The uses are practically unlimited. You can cure illnesses and conditions which are very dangerous. Alzheimer’s disease, heart disease, diabetes, multiple sclerosis, AIDS, and arthritis are easier to treat with genetic engineering. Also the food problem in some countries has been solved or at least postponed thanlks to it. n fact, about 60 percent of our food has some sort of biotechnology in it; that is not necesarily good. By taking traits from one organism and putting it into a food it can last longer, taste better, and grow faster and larger. It can also be designed to be more immune to certain diseases. Many industrial branches are using bacteria to produce chemicals and also many other uses. But there are risk. The food could be altered or it could lack vitamins. When used careless it could do more damage than good with certain diseases. But hopefuly people are going to learn how to control this type of technology and use it to aid mankind.