An arbor is typically a two or four-post trellis framework with a lattice and/or arched top. An arbor typically covers the entrance or exit of gardens or yards, or defines the transition of one outdoor area to another.  Arbors can also be used as accent structures. A pergola is typically a structure with multiple columns, either attached to a home on one side or free-standing. It’s meant to provide an area for people to sit under and, in some cases, it provides shade.  A pergola can also be an accent in an outdoor area.