Good afternoon Zahra.
An abstract for anything is just that; an abstract. This is a rough outline of what your paper will cover, with very few details. Your topic should be stated, and any other major important details (i.e. if you use statistical data, clinical trials, etc.). You don't want to include too much information, and keep it simple. You may try searching the internet for article abstracts, there are millions out there to give you finite examples.
Good luck!
Regards,
Gloria
Moderator, EssayForum.com
Gloria, EssayForum.com