On many occasions, the wood of your deck will be exposed to water, and in fact, wooden deck and wood siding are usually exposed to a great deal of water in their lifetime. Meanwhile, staining your deck will form a barrier over the surface of the wood and make it resistant to water. Therefore, water will flow away without harming the wood.
Wood usually is susceptible to rotting. Rot is a significant threat to wood because once the wood rots, the damage cannot be reversed, staining the wood of your deck will protect it from termites, mold, and mildew.
Repeated exposure of deck to sunlight can damage the wood. The only way to protect your wood in your deck is by staining it to keep it from being discolored and damaged.