From the website:

TripAdvisor is the largest travel community in the world, attracts more than 24 million monthly visitors. TripAdvisor.com features real advice from real travelers, with more than 5 million unbiased reviews and opinions, covering 250,000+ hotels and attractions and operates sites in the U.S. and in the U.K. The TripAdvisor media network provides travel suppliers with graphical advertising opportunities and a cost-per-click marketing platform.

Currently, there are about 24 million monthly visitors on TripAdvisor, and features over 10 million user-generated reviews and opinions