A CRM is a tool that helps you to manage leads(A clients and a lead are not the same) in an ordered fashion to better follow up and improve the sale success.
!!Important!!A CRM is used by businesses that have a long sales cycle .
In a CRM you'll find different functions that will help you manage the relationship with the leads like record agreements, activities and interactions, create reminders, forecast the sale and identify the lead stage and even send emails.