What is the difference between ERP consultants and ERP implementation consultants and pre-sales consultants?

The difference between ERP consultant and ERP implementation consultant and pre-sales consultant: consultant is a kind of consultant selected according to the company's own nature. As a reference of ERP company, it is required to be familiar with management methods; Implementation consultant is a consultant hired for a problem to be solved after the relationship between users and suppliers is reached. This requirement is familiar with ERP itself and is generally provided by suppliers; Pre-sales consultant is a position established by ERP company in order to understand our products, explain the functions and details of our products to customers and ask customers to be familiar with their own products.