GApps (Google Apps) Android 6.0.1 (Marshmallow) refers to the proprietary packages containing Google's core mobile services (like the Play Store and Google Play Services) intended for custom ROMs.
XDA Developers BitGApps was designed for devices with small /system partitions (e.g., Moto G 2014, Galaxy S4 Mini). It uses heavily optimized, compressed libraries. gapps android 6.0.1