CMS (Content Management System) allows you to self manage content of your website by your own, at any point in time you can easily add videos and edit content of your website.
CRM (Customer Relationship Management) is a platform which allows you provide services to your customer. CRM enables you to have a more integrated model for communication with your customer, hence allowing you to strengthen your relationship with your customers.
ERP (Enterprise Resource Planning) is a system which allows you manage & strategically plan the inflow and outflow of your SKUs inventories. ERP also helps you to manage human, physical & financial resources of your business.