Overview of API

Application Programming Interface and is a set of code and standards for accessing a Web-based application or service. API thus allows a web application to interact with other applications programmatically similar to the way human accesses a web application via GUI within web browsers. By exposing their functions or content via API, web applications allows developers to easily enrich their sites with new features.

The diagram below shows how APIs act as important building blocks for next generation web applications

Lead Conversion

When a lead is converted, Account,contact and Opportunity will be created.When you convert leads, Salesforce creates new accounts, contacts, and, opportunities using information from the leads you’re converting.You can’t view converted leads, but they appear in lead reports. Salesforce updates the Last Modified Date and Last Modified By system fields on converted leads when picklist values included on converted leads are changed.