When you are protecting your blinds, you are usually playing into someone's bluff. Or so you assume.

I have the big blind. The whole table folds around and the small blind raises. This is a typical move late in a tournament. He is often just trying to steal you big blind. But often, I will call whatever raise he offered, especially when I have a bigger stack. I am protecting my blinds, or making sure they aren't stolen.

Overall, it's not a great idea to protect your blinds. Expecially if you are new-ish to holdem and don't have a lot of hands under your belt.