You can use the User Field when you want to show a list of users for someone to select from.
Selecting Multiple Users
In the Design Form section, you can make changes to this field. If you click on Allow selection of Multiple Users, then the person filling out the form can select more than one person.
If you select the option to Include Groups along with Users, the field will then also display groups. If you choose to display groups, you will not be able to apply any filters.
By default, the User Field will display all the users in your organization. You can limit the users displayed using a filter. You can filter based on the department, group, location, email domain, or individual email address. Filters can be made to match any condition (OR), or all conditions (AND).
For example, you can create a filter to only show users from a particular location. Then only those users appear in the field.
Using a Formula
You can also use a formula to auto-populate an email to display in the User field. However, if you use a formula, you will not be able to use any filters.