A lawful permanent resident (green card holder) can live and work in the US permanently. There are different ways through which you can come to the US. It depends on the intention of your visit. Visas and green cards help you come to the US legally.
You can enter the US through an through an immigrant or non-immigrant visa depending on the intention of your visit. You can visit the U.S. for tourism, study, or work through the non-immigrant visa and should your intent be permanent residence, the solution is an immigrant visa.
Having a green card simply means that you are legally granted immigration benefits to live and work in the United States. You can apply for a green card while you are in the US or abroad. When you get a green card while being physically present in the US, it is called adjustment of status. If you get it when you are abroad or when you are ineligible to adjust status, it is called Consular processing.
After you get in to the US on a visa, you can then adjust your status to a green card holder (permanent resident). But this is not applicable to all visa holders. It all depends on the visa category through which you entered. There are many ways to get permanent resident status. One is through your family member, who as a US citizen or a green card holder can sponsor you for green card status. Another option is the DV (Diversity Visa) lottery program that is conducted annually. Through this program, around 55,000 applicants are selected based on fulfilling certain simple but strict eligibility requirements. You can also get a green card through a job offer. To qualify under this classification, a qualified US employer has to sponsor you. Even if you are granted Refugee Status or Asylum, you can apply for a green card. It is important to remember that the process and procedures of getting a green card differs depending on the classification you are applying under.
Many persons mistake a conditional permanent resident for a permanent resident. A conditional permanent resident, who got a green card through marriage will get a card that is valid only for two years. He/she has to remove the conditions 90 days before the card expires. Another factor is that a conditional card cannot be renewed. If the conditions are not removed, he/she will lose his/her resident status. Form I-751 needs to be filed to remove the conditions and once the conditions are removed, a permanent resident card that has validity for the next ten years will be issued.
Getting the green card replaced/renewed :
As mentioned earlier, a permanent resident card comes with a validity of ten years and has to be renewed on its expiration by filing Form I-90 with the USCIS. Form I-90 is also used when you want to change any biographic information on your card i.e if your name has changed because of marriage. If your card was lost/stolen, the same process is followed. Being a green card holder makes you eligible for citizenship as permanent resident status is the main eligibility requirement for Naturalization.