Hello, your question is extremely vague, the internet itself is not a company and thus you do not have any "profile" other than your IP address, if you mean having a profile on a social networking site such as myspace, facebook, etc. - then there is a lot at stake, it means that whatever information you put there is available to be viewed by anybody on the internet (most times) - a lot can be found out about you also by who you choose to add as your friends, which details you list, etc. - I conducted a recent experiment that showed the ability to get a home address, phone number, and other details about a person and their family, from their myspace page, by searching directories using the details (home town, surname, date of birth) found on their profile.
It is always important to speak with a responsible adult before putting anything on the internet if you are not an adult yourself.