hi Nagaraju, Salesforce has its training documentations that will help you learn integration step by step: https://developer.salesforce.com/page/Integrating_with_the_Force.com_Platform
To learn te different APIs, dig deeper in the API guides available.
https://developer.salesforce.com/page/Integrating_with_the_Force.com_Platform
To learn te different APIs, dig deeper in the API guides available.