User Roles, also known as Security Plans, are a means of creating different levels of website access for different users. Each and every user is assigned to a role/security plan.
There are two types of roles/security plans: internal and external. Internal roles/security plans are designed for you and your employees. External roles/security plans are designed for your customers. The only core difference is that when an Internal role/security plans logs in, they are not associated with any particular customer #. They have to "become" a customer before doing part/catalog searches. External roles/securty plans are directly associated with a customer account.
By default, your website is equipped with a set of roles/security plans that are ideal for any ecommerce store. You do not have to utilize all of them. In fact, most of our customers only use 2-3 roles/security plans. You can also create an unlimited number of your own, custom roles/security plans. Please see attachment for details on how to create and edit these plans.