Understanding what a CRM is and what it is used for is fundamental in marketing automation.
This is an excellent article from a non-biased source on CRM basics.
Below is a quote but please click on the link below to read the complete article.
CRM stands for Customer Relationship Management, so by definition, a CRM is an app that helps you manage your relationships with current and prospective customers. Your email and address book already do that, in some ways—your email links related messages together, and lets you find all messages from a contact with a quick search, while your address book can hold as much info about your contacts as you want. Even the old-fashioned Rolodex was a CRM of sorts. But a true CRM should do a lot more than that, t
Source: The Beginner’s Guide to CRM: Customer Relationship Management – The Ultimate Guide to CRM Apps – Zapier