All 3 Uses of

arbor

in

To Kill a Mockingbird

Our tacit treaty with Miss Maudie was that we could play on her lawn, eat her scuppernongs if we didn't jump on the arbor, and explore her vast back lot, terms so generous we seldom spoke to her, so careful were we to preserve the delicate balance of our relationship, but Jem and Dill drove me closer to her with their behavior.
p. 47.2

arbor = a framework that supports climbing plants

Jeremy Finch, Maudie Atkinson told me you broke down her scuppernong arbor this morning.
p. 116.8 *

Jem, who hadn't been near Miss Maudie's scuppernong arbor since last summer, and who knew Miss Maudie wouldn't tell Atticus if he had, issued a general denial.
p. 116.9

Definitions:

(1) (arbor as in: shaded arbor)
a framework that supports climbing plants; or a shady rest area made by such a framework or by trees and shrubs

The framework of an arbor is generally thought of as a wood lattice made to support vines, but it can also be a natural framework such as trees.
(2) (meaning too rare to warrant focus)
Much more rarely, an arbor can be used as a proper noun to reference a location. As a common noun, it can also reference various types of rotating machine shafts.