A green card is a card that shows proof of your legal permanent residence – your right to live and
work permanently in the U.S.

You can get a green card by being petitioned by your relatives (in a process known as family-
based immigration), or by an employer (in a process known as employment-based immigration).

If your family member is a U.S. citizen, they can petition a spouse, a child, and siblings (brothers/sisters). If you are a child of a U.S. citizen, you can be petitioned whether you are married, or unmarried. If your family member is a legal permanent resident (i.e., has a green card), they can only petition their children under the age of 21 and their spouse. The children cannot be married.

An employer can file a petition on your behalf which, if approved, will allow you to file an application to obtain a green card. Before they file the petition on your behalf, they have to obtain a certification from the Department of Labor indicating they cannot find any U.S. workers who are able, willing qualified, and available to perform the job that is being offered by the employer.
 
To obtain the labor certification, an employer must, among other things, advertise for the particular job opening and interview potential candidates qualified for the job. The specific number and types of advertisements are indicated in Department of Labor regulations and depend on whether the job involves a professional occupation (i.e., an occupation that requires either a bachelor’s or higher degree) or a non-professional occupation (an occupation where a bachelor’s or higher degree is not the usual requirement for the occupation). If they cannot find a U.S. worker who is able, willing, qualified and available to perform the job, they can then file a Permanent Labor Certification Application with the Department of Labor. If approved, they can then move forward with the filing of a petition for you.

If you obtained your green card through marriage to a U.S. citizen and have had it for three years, or if you obtained your green card through other than marriage to a U.S. citizen and have had it for five years, then you can apply for citizenship 90 days prior to the date you have had your green card for the indicated time above (i.e., five year or three year period), assuming you have been continuously residing in the U.S. for that period of time, have been physically present in the U.S. at least half of that time, and meet all of the other requirements (for all requirements, click the following link: Citizenship/Naturalization Services)

If you apply to obtain a green card through marriage, but you have not been married at least two years, you will obtain a conditional green card. The card is only valid for two years. You must file a petition within the 90 day period before your conditional residence expires to remove the conditions, and include evidence of a bona fide marriage. If the petition is approved, you will receive a permanent green card. If the petition is not approved, you will lose your conditional residence status and will be subject to removal from the U.S.

In order for an employer to file an immigrant petition on your behalf, they need to include a labor certification issued by the Department of Labor with the petition. The labor certification is a document issued by the Department of Labor after an employer proves they cannot find any U.S. workers who are able, willing qualified, and available to perform the job that is being offered by the employer. They apply for the certification after they, among other things, advertise for the particular job opening, interview potential candidates qualified for the job, and cannot find a worker who is able, willing, qualified and available to perform the job.

In general, by itself, the H-1B visa will not allow you to obtain a green card. However, while working for an employer, the employer can get to know you and the quality of your work well enough such that they may want you to work for them on a permanent basis. They can then take steps to file a petition on your behalf.

The maximum time you can be in H-1B status is six years. The H-1B visa is initially granted for a period of three years and is renewable for another three years. After the six year period, unless you are eligible for further extensions (see question below), you must leave the U.S. for at least one year to reset the clock and be able to work in H-1B status for another total six years.
 
The six year period relates to how long you are in H-1B status in the U.S. The time you spend outside of the U.S. does not count towards your six year maximum. Therefore, if you go to your home country, for example, for a vacation, the time spent there will not count towards your six year maximum. You (through your employer) can apply to recapture this time not spent in H-1B status to ensure all of your six year period is utilized.

Under the American Competitiveness in the 21st Century Act § 106(a), an H-1B visa holder can extend their visa for more than six years (in one year increments) if they are the beneficiary of an employment-based petition or a labor certification and if at least 365 days have passed since the filing of the immigrant petition or labor certification. Under the American Competitiveness in the 21st Century Act § 104(c), an H-1B visa holder can extend their visa beyond the sixth year (in a maximum of three year increments) if they are the beneficiary of certain employment-based petitions and are eligible to obtain a green card, but cannot do so yet based on country visa limits. They may obtain extensions until their application for a green card (application to adjust status) is adjudicated.

Under the H-1B portability provisions found in INA § 214 (n) and 8 CFR § 214.2(h)(2)(i)(H), as long as you have been lawfully admitted to the U.S., your new employer files a non-frivolous H-1B petition for new employment on your behalf before your period of authorized stay expires, and you have not been employed without authorization from the time of your last admission through filing of the new petition, you can begin working for your new employer and continue to work for them until the petition for new employment is adjudicated.

Under INA § 204(j), you can change your job/employer as long as your adjustment of status application has been filed and pending at least 180 days, and the new job is in the same or a similar occupational classification as the job for which the I-140 petition was filed. It is best to do this after the I-140 petition is approved. Moreover, since your petitioning employer can revoke the I-140 petition up to 180 days after it is approved, it is best to wait at least 180 days after the I-140 has been approved before requesting job portability under INA § 204(j).