The main service that you use to handle calls for your company may be a CRM platform such as Salesforce, Microsoft Dynamics, or Zendesk.
Your system may be set up such that the Contact application has been integrated with the CRM platform that you use, to enhance the overall CRM capability of your company. In this instance, you continue to use the CRM platform as your main environment, but you can log into the Contact softphone within your CRM platform and then use the Contact to make and receive calls.