What is the difference between EDMS and ERP?

EDMS is Electronic Document Management System. with the help of that you can manage and secure your Doucment. ERP (Enterprise resource planning) is business process mangement software that allows an organization to use a system of integrated applications to manage the businss and automate many back office functions related to technology, services and human resources. 

EDMS will help to manage doucments only but through ERP you can automate your business

EDMS - electronic document management system manages documents, scanning, storing retrieving - in some cases gleaning data and transferring that information to other systems.

ERP - Enterprise Resource Planning & business setup in all areas like Finance,Sales,Costing and materials etc.