Contacts are people with whom you communicate, either in pursuit of a business opportunity or for personal reasons. In Business-to-Consumer (B2C) scenarios, contact is the most important information for acquiring customers, whereas in Business-to-Business (B2B) it is a part of the organization details with which you are doing business.
The most important function of the contacts module in Zoho CRM is that they can be used for both customers' acquisitions as well as procurement of products from the vendors. Contacts can be related to an account as well as vendors according to your business process.