The star rating system is a yard stick for a hotel's overall quality. The star rating pertains to a hotel's level of service, facilities, rooms, location, price and other amenities.
Tripadvisor (TA) is the rating of the hotel given by the guest basis their individual experience. For instance, a 3-star hotel can have a 4.5 TA rating, which means that majority of the users are happy with the hotel.