Below a diagram to explain dependencies between Tenant, Company and Account.

When you create an Order as a CSR User (Tenant contains Users with different roles like CSR, Dispatcher, ...) you need to choose an Account and a User in this account. It means that you will create an Order on behalf of this User for his account (account contains Users, named Self served users, with or without admin role). Illustrated below:

When you create an Order as a User (self served User) this step is skipped because you already are a User, linked to an Account.