Many foreign nationals wrongly believe that Green Cards and works visas are both the same but both the documents are different and represent different statuses.
United States Green Cards
US Green Cards are Alien Registration Cards, that were once green in color and these cards will help the foreign nationals who are granted lawful status, to prove their status. Permanent resident status comes with several rights and this status will permit foreign nationals to legally live and work where ever they wish, in the United States. After being granted lawful status, a foreign national can help his/her family members to obtain Green Cards. Similarly, they can become US citizens within five years, if they meet few requirements. Moreover, people who hold Green Cards need not obtain employment authorization documents to work in the country.
The only thing that the Green Card holders must do is to make the United States their permanent home as the country grants lawful status only to the individuals who seek to settle in the country. If they obtain US Green Cards and reside in foreign countries, they will lose their status and their Green Cards will be revoked. Likewise, they must not spend more number of days in foreign countries though they are allowed to travel to foreign countries and they must understand that there are limitations and remember that they can remain abroad only for a certain period of time.
Similarly, these Green Cards come with expiration dates and the permanent residents must keep renewing their cards every ten years and that is something that the permanent residents must not forget to do. However, this does not mean that the permanent resident status is itself valid only for ten years and only their Green Cards must be renewed and replaced every ten years. However, this does not apply to conditional residents who hold two year cards as these cards cannot be renewed and their status will expire if they fail to take necessary steps to convert to lawful permanent resident status.
United States Work Visas
A work visa will only permit a foreign national to work in the country and he may not be able to reside permanently in the country if he gets into America on a work visa. Similarly, to get a work visa, a foreign national must be sponsored by a US employer. As long as the visa is valid, the foreign national who holds the work visa can work in the country and with a work visa the foreign national can work only for a particular employer.
These work visas will be valid only for a certain period and will expire but the permanent resident status granted Green Card holders will not expire. However, there are several types of work visas that would permit foreign nationals to work in the country on a temporary basis and people who seek to work in America temporarily may obtain work visas. But people who wish to permanently work in the country must go for Green Cards. A Green Card will permit the holder to live permanently in America and it is a kind of permanent employment status. You may not be granted legal status, if you get into the country on a work visa but a Green Card means that you are a legal resident of the country.