Your profile is your own personal space... You should control who is allowed in!

Your profile is your own personal web page. You can choose to display as little or as much information as you like here and include things such as a profile picture, information such as your birthdate or even your religious or political views.
As well as choosing what information you want to display, you should think about who you want to be able to see what you publish on your profile. One way to think about this is - if you publish any information to 'everyone', you might as well write it on a big sign and wander through town. If you wouldn't be happy showing everyone you might bump into, make the information viewable to 'Only Friends'.
Another useful thing to check out is who can see tagged photos of you.