In a nutshell, customer relationship management (CRM) software handles customer profiles and keeps track of any customer orders and correspondence.  It’s basically a record of your relationship with a potential customer.
CPQ systems help you build and quote orders for customers that exist within your CRM database.  If you’re using a CRM, CPQ works alongside this tool to help you create accurately priced quotes for your customers.  The CRM can then hold a record of those quotes, along with the customer’s purchase history, so that you can refer back to it later.
If you don’t already use a CRM platform, some CPQ tools may provide support.  PandaDoc offers an onboard CRM that works natively with the CPQ model to streamline signing and sending, but it lacks the robust functionality of a dedicated CRM like Salesforce or Insightly.