When I Google images of cars, I always see these great 'concept' cars, but I never see such cars being sold? What is the purpose of these cars?
There are many purposes for a concept car to exist.
New direction for company: A concept car might very well be a bold new design direction that a company wishes to go in, but needs public opinion on first. The concept helps to gauge market reaction, and since the market dictates sales, a concept car can be hugely integral to a company's success.
New engineering ideas: A concept could be a way to showcase new ideas brought upon by both the design and engineering departments within the automaker itself.
Anniversary specials: A concept car could very well be a gift to the company itself to celebrate an anniversary or special event.
Production car preview: This, in stark contrast to generations before, tends to be the most common theme nowadays. Most car makers will show a concept to "tease" the crowd and make them ask about it. Sometimes however, this can be quite the bad idea, because while it saves the automaker money on re-engineering and design efforts, if the design is not well received by the public, it can preview what will soon come to be a sales flop.
- to let designers having fun (designing and drawing sedans isn't that fun, you know, so they can get crazy on concepts), a great example of this is Rinspeed:
They are not meant for production but as vehicles to try out new ideas and see what shape they take and what the public reaction is. They are usually shown at Auto shows.