1. As the name suggests, it is the integration of Photovoltaics into the building envelope. Here the PV system provides two functions; it acts as the building skin and it produces electricity.
2. Building-integrated photovoltaics are photovoltaic materials or components that are used in place of traditional building components or materials, especially in building features such as facades, roofs or skylights, and provide solar power for the building.
http://www.solarmango.com/dictionary/bipv (1.); https://www.techopedia.com/definition/31044/building-integrated-photovoltaics-bipv (2.)