i want to live and work in the usa,but i need a green card and i dont know what this is..can you tell me?

Answer 1

A united States "Green Card" (which is not green in colour) is a permanent residency visa. There is, as the previous answerer mentioned, a "green card" lottery, which issues 50,000 a year, but not all countries are allowed to enter it, and so many people DO enter it, the chances are miniscule ... and still subject to being eligible for entry. However, a small chance is better than no chance, eh?

There are also other ways of being granted a green card, such as being sponsored by relatives who are citizens or permanent residents of the U.S. being sponsored by an employer, and other ways as well. You can find the information here:
http://www.uscis.gov/graphics/
http://usimmigrationlaws.net/

Answer 2

The Green Card is a special visa that allows people to work in the USA. However, they are very difficult to get. The US gives out 50,000 every year. If you want one, you have to register, and then you are put in a lottery along with every other person in the world who wants one. They then randomly pick out 50, 000 people, and they get the cards.
Try this site for more details:

http://www.official-green-card.org/