This REST API allows you to manage accounts, leads, and custom objects while interacting with Force.com. Recommended use is with mobile applications and Web 2.0 projects to create, retrieve, update or delete records in the Salesforce directory. Salesforce is a customer relationship management services company.
You can learn to build an app using the Salesforce API that gives you a customer's name, email, and phone number. The API can help you to access leads information and understand client behavior. Web actions like click, watch, scroll, browse can determine how a sales team can follow up.