Complex sentence: The ArcGIS Pro application was added to ArcGIS for Desktop in 2015, is comprised of the combined capabilities of the other integrated applications and was built as a fully 64-bit software application.
Split into simpler sentences: The ArcGIS Pro application was added to ArcGIS for Desktop in 2015. It had the combined capabilities of the other integrated applications and was built as a fully 64-bit software application.