Consular Processing is another way to obtain your green card. If you are in the US you can adjust your status, whereas if you are outside the US, you have to go through consular processing at a U.S. consular post abroad for an immigrant visa.
Once you get the visa, you can come to the US as a permanent resident, and your green card will be mailed to you similar to if you had you adjusted your status in the US.
If you going through consular processing, the USCIS will forward your approved preference petition to the National Visa Center (NVC). The NVC will then send you a package that contains forms, document list and instructions. The completed package is returned directly to the NVC.
If the application process is complete and if visa numbers are current for your preference category for your country of birth, you will be sent a notice regarding your appointment and it will include more forms and instructions.
During consular processing, you have to attend a personal interview for you and your dependent family members will also have one at the US consular post. As appointments are scheduled on short notice, ensure that you are ready and able to travel when the appointment has been scheduled. In addition, you should take a medical examination with a physician approved by the U.S. consular post.
Though the documentation required for visa processing is more or less similar to that required for adjustment, there are a few exceptions. For consular processing, you have to provide a police certificate of good conduct from each country in which you, or a family member resided for six months or more since the age of 16. You must also provide evidence of having fulfilled any obligatory military service.
Consular processing is considerably quicker than adjustment of status and can take as little as six months to complete. However, it is important to remember that the process takes place outside of the US, so if there is any problem with the application, you may not be able to return until it is resolved. Another fact is that there is no formal appeal process for immigrant visa applications as there is for Adjustment of Status applications.
Apart from this, you have to maintain your US non immigrant status while the application for an immigrant visa is pending. Neither you nor your family members are eligible for EAD cards or Advance Parole.