To explain parody i may have to explain pastiche first. Pastiche is an imitation of a style that has previously been used. It is basically a copy of another artists working methods to produce similar results. A parody on the other hand is a pastiche which is mocking the original piece of work while keeping curtain aspects the same.
Parody is different to a pastiche or homage as it is not copying the work or the style to every detail but it is taking the subject matter then changing it in its own way to appeal to a new audience. It could be seen as breathing life back into a dormant piece.
There are many examples of parodies we see around us everyday. Parody is typical in contemporary comical films but can be found everywhere. For example below is the poster design for the first Star Wars film to be made called "A New Hope".
A comedy series called "Family Guy" then produced a parody of the film years later (this is also referred to as a spoof film). As well as doing their own version of the film they also parodied the poster design to produce their poster / front cover that you see below. The connections are clear so the audience can make the connection between the two films but see a twist has been made.
As well as this "Family Guy" version another has been produced by [adult swim] which is also along the same lines. It keeps the story and important details the same but just delivers them to the audience in a different manna.
Parodies are very popular with the public nowadays as parody films are being made all the time. Some are regarded as a dedication to the original piece where as some may just take the story and put a new take on it. In film this can be used as a clever technique to attract a wider audience as fans of the original as well as the new version will all join together to see the new piece. Parodies can seem a lot more personal to the audience as they can relate to the original piece giving them the satisfaction when connection the two.
I believe that parodies keep the original works alive as they keep audiences interested rather than letting them forget and move on. Both pastiche and parody are very similar and can both achieve this same goal. In an ever changing world techniques like these help cement the originals in history.