Functions are fields of activity of a company.
Under Settings - Contacts - Features you can create a new function.

Simply enter the name in the input field and then click on Add. 
All functions in your company can be deleted here trash_01 as well as edited edit_01 .

Now how do you add a role to an employee?

First, use the search function to find the contact you want.
Then in the contact information on the right select the tab Features .