"Unlawfully present" has a complex definition. Generally it means that either you entered without a lawful status or you remained beyond your authorized stay. You may not have been unlawfully present during periods where you had TPS, were in duration of status (e.g. if you entered on a student visa or as a Canadian visitor), had an I-485 pending, or had an asylum application pending. Time before April 1, 1997 does not count. Other exceptions apply. Time and entries occurring before you turn 18 will count.