You have your I

You have your I-485 Receipt........

Your application for adjustment of status is pending with the USCIS
You have applied for immigrant status
Your application is based on the labor certification and preference petition filed by your employer (or your spouse's employer)

Your application for adjustment of status will be abandoned, unless you either have an approved "advance parole" before you leave, or you are currently in H or L status, and reenter the U.S. in valid H or L status - using a valid H or L visa. (Visa requirement does not apply to Canadians.)

You must maintain your permission to work in the U.S.
If you have an H-1b, it may be renewed while your I-485 is pending
If you have an EAD, you may work on the EAD
If you work for an employer other than the one sponsoring you for your H or L status, you must have an EAD.
If you work on the EAD for an employer other than the one sponsoring you for H or L status, your H or L status is no longer valid.

If you have a valid H-1b, or L-1 visa in your passport, you may use it to return to the U.S. to continue your H or L status - and do not have to use your advance parole to come back.
If you are an H-4 and have worked in the U.S. on an EAD, you must use your advance parole, and not your visa, to return to the U.S. If you have not worked, you may return to the U.S. without the advance parole, using your valid visa- provided your spouse (parent) is maintaining their H-1b status.
If you are an L-2 and have worked on an EAD that you obtained as an L-2, and that EAD is still valid, you may return to the U.S. using your visa. However, if you have worked based on an EAD you obtained with the filing ofyour I-485 - you must use the advance parole to return, and not your visa. If your spouse is not maintaining L-1 status, you must use the advance parole to return to the U.S.
If you work in the U.S. for an employer other than your H-1b or L-1 sponsor, you MUST use the advance parole to return to the U.S., and you must have an EAD to continue working.
If you are an L-1 or an H-1b and return to the U.S. using your advance parole, your spouse and children can no longer travel using their L-2 or H-4 visas - they must have advance paroles.

If you leave the U.S. and apply for a new H or L visa, you may return using that visa instead of the advance parole
If your H or L visa has expired, and you don't obtain a new visa while abroad, you can only return using your advance parole.

If we applied for an EAD on your behalf, it should be approved in 90 days or less.
Advance parole processing time may be checked here: the USCIS for approximate processing time.
If your company's I-140 has not yet been approved, we anticipate it may be six months to one year before it is adjudicated.
If you don't yet have a social security number valid for employment authorization, you can apply for one based on your approved EAD. It may be several weeks after the EAD is approved before the Social Security database is updated with information from the USCIS database.