Until version 2018.2, Orbeon Forms shipped with 3 "dropdown" components:

• A plain dropdown where the possible values were provided by the form author.
• A plain dropdown where the values were loaded from a service.
• An "autocomplete" that enabled users to type in the field to do a search, with Orbeon Forms sending what the user searched for to a service, and displayed the result.

Those components conflated the following characteristics:

• Whether the possible values are entered statically by the form author, or loaded from a service.
• Whether the control shows as a plain dropdown, or as a dropdown allowing users to type text to search for a value.
• In this latter case, when users can type a search value and values are loaded from a service, whether the service returned all the values and the filtering is done by Orbeon Forms, or if the search term is sent to the service and it is the service that does the filtering.

Since version 2019.1, Orbeon Forms makes those characteristics orthogonal, allowing you as a form author to combine them in any way you want. Moreover, for services that perform the search, services can also implement paging, in cases where the list of possible values can be very large, even when filtered by something the user has typed. All the possible combinations are summarized in the following diagram: