You can enter simply the name or dates and places if you have them as well. It will bring up anyone that matches that criteria, and hopefully you will find other family member's names and dates related to that person. In some case people have also posted stories and information about people, which I truly love. Not only do I want to find my ancestors, but I also want to know more about their life if possible.
Give it a try. Start with you grandparents and see if you don't uncover something you didn't know, or people you didn't know existed.
There is also Ancestry.com which you can find a lot of information on and is a very useful tool in your search. I have found it really cuts your search time in half, but it costs about $200 per year. I used their two week free subscription and really got the ball rolling on my search, but I can't afford their site right now.