SOAP and RESTful web services allows a client to query server for some information, but the way they are implemented and used is quite different.
The main difference between SOAP and REST is that former provides an standard of communication between client, server and other parties has restricted set of rules and format, while REST leverages ubiquity of HTTP protocol, in both client serversand, to allow them to communicate with each other regardless of their implementation.
In short, getting data from a RESTful web service requires less headache then getting data from a SOAP web service.
Since everybody is familiar with HTTP requests like GET or POST, its easy to understand and correlated how RESTful webservice are working and which URL of REST web service provides what kind of information. In SOAP, you need to understand lengthy WSDL document to find out right methods and right way to call them.
Here are some fundamental differences between REST, RESTful and SOAP Web Services, which will help you not only to understand these two key technologies better.
REST stands for REpresntational State Transfer (REST) while SOAP Stands for Simple Object Access Protocol (SOAP).
Architecture style vs Protocol
REST is an architectural style, on which RESTFul web services are built, while SOAP is a standard devised to streamline communication between client and server in terms of format, structure and method.
Use of HTTP Protocol
REST takes full advantage of HTTP protocol, including methods
Processing a RESTful web service request is much faster than processing a SOAP message because you need to less parsing. Because of this reason RESTful web services are faster than SOAP web service.
SOAP messages consumes more bandwidth than RESTFul messages for similar type of operation because XML is more verbose than JSON, standard way to send RESTFul messages and SOAP has additional header for every message, while RESTFul services utilizes HTTP header.
Security in RESTful web service can be implemented using standard and traditional solutions for authorized access to certain web resources. While to implement security in SOAP based web services you need additional infrastructure in web to enable message or transport level security concerns.