What is the difference between webservice and HTTP service? I have used HTTP service with REST api. But not able to understand what do we use webservice keyword and what is the difference between these. Can any one help me to understand these things better.
The difference is the "payload" of the body and some different headers. Both start off with the standard HTTP format:
ACTION PATH VERSION Header: Value <repeat-as-necessary> <body>
From there, they differ in how they are used. REST typically uses JSON, while SOAP uses XML with certain required formats.
SOAP is more bandwidth intensive than JSON, but tends to have better support in older software. There is a WSDL format that specifies how the SOAP messages should be formed, leading to quick development times (but, arguably, JSON is just as fast in most cases).
Normally, you'll choose the protocol based on your needs, usually determined by which format your programming language supports and the features you need to access from the service (SOAP and REST may not always offer the same API calls). Use REST when no other factors dictate a choice, and leave SOAP (webservices) if you need to use it.