A competitive analysis (sometimes also called compartive analysis or benchmarking) is the process of analyzing products which are similar to, or compete with, the product you are designing in order to generate ideas.
Try using similar services or products in order to find out:
Current trends in the marketplace
What expectations your users will have
What to do, what not to do
"Must have" standard features
Sometimes it can even be helpful to have your users test comparable products they currently use or could potentially use in order to understand how these products succeed in or fail to help users achieve their goals.