An arbor is a shade feature included on some decks that is supported by at least 2 posts and is usually somehow integrated into the rail system.
An arbor usually consists of an assembly of a wood beam attached across two upright posts with smaller louvered members spaced across the top to provide shade and or a place to hang plants.
Arbors are similar to pergolas but are usually quite narrow and are less enclosed.
It is a common detail to add a decorative cut to the ends of the beams and louvers.
A good arbor separates itself from others in the attention to details.
How do the pieces relate to one another and how to they physically connect?
Search out some pictures on the internet until you find a design that appeals to you.
Arbors should be strategically located on the deck to reduce harsh sun angles and enhance the comfort for the space.