A personal statement depicts your aims, ambitions, skills and vision for future. It is an opportunity to sell yourself in the corporate world. It could be general and comprehensive or a response to a specific question.
You must state what is special, unique, distinctive or impressive about you. Remember that the job hunters or college heads are looking for a person who is unique and has a potential for change so you must show them that you are the one.
Here is a link that will help you out in writing your personal statement.