posted 10 years ago
That's a big subject that I'm not sure can be adequately addressed in a forum like this. To make it as succinct as possible off the top of my head: "to allow processes running on separate machines to connect to one another over a network, irrespective of their (possibly differing) operating systems, implementation languages and other hardware and software characteristics they may have (and which may change over time)".
You may wish to search for "what are web services" or some such phrase to find introductory articles that explain them in more detail.