Yes. The Pega Knowledge application includes the ability to create not only knowledge self-service sites (Pega Knowledge Help Sites), but also community sites. Details on the Pega Community (via Pega Knowledge application) can be found in the Pega Knowledge Product Overview document and the Pega Knowledge User Guide.
The Communities configuration tools are provided in the Pega Knowledge authoring portal, with the ability to quickly configure and publish a branded Community site where your external (or internal) members can collaborate. Please read through the Product Overview for details.