REST is a light-weight implementation of Web Service, which evolved from other distributed architecture solutions, such as CORBA, RMI, COM/DCOM, SOAP, SOA with XML. Here is a brief report on the history of Web Service: http://bit.ly/1jkySqU

But instead of XML, it employs data format of JSON to reduce the data size and every time it only returns a portion of the data, instead of return a complete set of data according to XML schema. This saves a lot of time for fast communication, especially if the application data set is small and simple, such as chatting.

But one interesting question is: Axis has one mode using RPC call, which is pretty fast and flexible based on SOAP using object serialization. But it's no longer popular now. Do you know why? There is a little trick of the object serializing when passing the parameters, though. But it can do RPC call so easily than the key/value pairs of JSON.