In the present multinational and multicultural world every art gallery tries to expand their marketplace by using the Internet.
The Internet is beneficial. When you are looking for an artwork to make your room look beautiful, you will definitely go to some neighboring art gallery. Yet in many cases you will have to be content with something they have, rather then with what you would like to have on your wall. The solution here can be in using some general art catalog, which exists in print or in the Internet (in rare cases both). There is no physical gallery that could allow itself to exhibit all items it has in stock.
Online is not limited in space, one can exhibit everything he has without caring for space it occupies. Online is better for inexpensive items, while a physical exhibition is good for expensive art, where people could see it in person.