Lawful status means that you have an unexpired Form I-94 (https://i94.cbp.dhs.gov/I94/#/home) or passport stamp that was issued by immigration authorities and are complying with the conditions of the specific visa. If you do not comply with those conditions, you will not have lawful status. For example, an H-1B visa holder who does not work for the employer that sponsored their petition, a person who comes over on a tourist visa and works, or if you overstay the date you are authorized to stay, you do not have lawful status. By contrast, a period of authorized stay is the time during which you do not have lawful status but have permission to stay in the U.S. for a certain reason. For example, when you apply to extend or change your status before the expiration of your current status but USCIS does not make a decision on your application before your status expires, you will be in a period of authorized stay.