Dry cleaning is different to washing
It's a process that cleans clothes without water. The cleaning fluid that is used is a liquid, and all garments are immersed and cleaned in a liquid solvent -- the fact that there is no water is why the process is called "dry.

Like many inventions, dry cleaning came about by accident.

In 1855, Jean Baptiste Jolly, a French dye-works owner, noticed that his table cloth became cleaner after his maid accidentally overturned a kerosene lamp on it. Operating through his dye-works company, Jolly offered a new service and called it "dry cleaning."

Early dry cleaners used a variety of solvents -- including gasoline and kerosene -- to clean clothes and fabrics. In the United States, the dry-cleaning industry is fairly new and has developed only during the past 75 years. Since World War II ended, the volatile synthetic solvents carbon tetrachloride and trichlorethylene gave way to a product known as perchlorethylene (perc), which became the overwhelming solvent choice for the industry. It was not only safer and faster, but did a much better job of cleaning, required less massive equipment, less floor space, and could be installed in retail locations offering excellent quality one-hour service.

As a result of this innovation, the majority of clothes today are cleaned by perc. A proliferation of cleaning franchises and dry-cleaning businesses offering fast service from convenient, clean, and attractive locations evolved to change the industry into what we see today.

With thanks to "How Stuff works"