Form, official instructions and conditions can be accessed there: https://www.uscis.gov/i-765.
When on a H-1B or other temporary visa, is may be a good idea to fill this form to request for an "Employment Authorization Document" (EAD). This document may take about 5 weeks to be received and can be used to work legally if the previous visa is expiring before the delivery of the green card, for example.
As a H-1B with for a concurrent filling of a NIW petition, here are some questions which might be problematic:
Header: I am applying for: [X] Permission to accept employment
Question 15. Current Immigration Status (Visitor, Student, etc.): H-1B
Question 16. Eligibility Category. (c) (9) [double check in the instructions that this category corresponds to the petitioners' case]
If the card takes more than one year to arrive, the petitioner may need to renew his/her EAD which is usually valid for 1 year. It is advised to apply for a renewal more than 90 days before the expiration date, but not more than 120 days before. In this case, the following answers may need to be adjusted
Header: I am applying for: [X] Renewal of my permission to accept employment (attach a copy of your previous employment authorization document)
Question 15. Current Immigration Status (Visitor, Student, etc.): H-1B (if still valid), or AOS Pending (if the application has been approved and the Adjustment Of Status is indeed pending), or.... etc...
Question 10. Alien Registration Number (A-Number). [This number appears on the top of the I-797 forms received that confirm that the green card application has been received]
Question 11. Have you ever before applied for employment authorization from USCIS?
[X] Yes
Which USCIS Office? Nebraska Service Center [or whatever the address was the first time]...