Arbors vs. Trellises: What's the difference?
Arbor: I look at an arbor as sort of a cross between the trellis and the pergola. It is generally a three-sided structure consisting of trellised panels on either side, and then an arch, gable, or pergola-like top comprised of wood beams. It usually serves as an entry point or passage into a garden or yard. Most simply, it’s smaller than a pergola but shelters to a similar extent.
Trellis: A trellis, by definition, is just what you see here, painted yellow and hung on the barn’s exterior. It is a lattice panel onto which plants may be trained to climb. In fact, the training of plants was its original, intended purpose though it was popularized as a decor element in its own right by the famous interior designer Elsie de Wolfe (link to my Houzz article on The Art of Treillage?)