Complex sentence: If tethering is done over WLAN, the feature may be branded as a mobile hotspot, which allows the smartphone to serve as a portable router; mobile hotspots may be protected by a PIN or password.
Split into simpler sentences: If tethering is done over WLAN, the feature may be branded as a mobile hotspot, which allows the smartphone to serve as a portable router. Mobile hotspots may be protected by a PIN or password.