Lots of people are here in Chicagoland from other countries, and they are not immigrants. Thousands visit Chicago from around the world on a tourist visa. While Americans can visit most countries without applying for a tourist visa in advance, the same is not true for most foreigners coming to the U.S. Others are here as students, or under a variety of employment visas. None of these people are "allowed" to have immigrant intent (with some exceptions like holders of O-1(b) or L-1 employment visas). They have to intend to return to their home country at the expiration of their visit, or employment assignment.
Many more people came here and are here to stay. Some came as a foreign spouse of a U.S. citizen or green card holder. Others entered pursuant to a fiancee visa granted for a U.S. citizen. Many siblings, parents, or children of green card holders and citizens become entitled to enter and obtain a green card after lengthy waiting periods. Foreign people with enough money are able to enter the U.S. and obtain a green card thanks to a substantial investment in a business in the U.S.
Sometimes people enter with a nonimmigrant visa, but then stay, and wind up "out of status." Sometimes people visit with a tourist visa, but then work. Sometimes people are here with a valid employment visa, but overstay past its expiration, and work without authorization. These situations cause the biggest problems for people, and like everything, are best treated early, or prevented if possible.
If you are here on a tourist visa, or a student visa, or if you overstay past your allowed departure date, don't work. Definitely don't put pictures of yourself working on the internet either. U.S. immigration has viewed a client's facebook page showing him teaching a lesson in the U.S. while here on a tourist visa. His visa was cancelled and he will have a problem getting back into the country.
U.S. immigration asked a man at O'hare airport if he had been working while in the U.S., and he answered "no." Then they asked to see his I.D., and it was his chauffer driver's license. He was returned to Jordan with a permanent bar to re-entry for misrepresentation.
One 24-year old was asked at O'hare if he had been working while here on his tourist visa. He answered "no." Then they asked him which kitchen he worked at. He told them the name of a business! Then they asked if he was paid, and three questions later, the kid admitted he was paid $40 or $60 sometimes for taking photographs for his brother-in-law's restaurant menu. He was sent back to Thailand with a five year bar for working without authorization.
A Buddhist monk who entered with a valid visa as a religious worker overstayed the expiration of that visa. He never got paid anything, but, because he was allowed to stay at the temple and get free food, he was found to have been working without authorization, and subject to removal.
A student with a valid F-1 visa from China at LAX airport was recently sent back to China with a bar to reentry when immigration took her phone, and scrolled through her instant messages with a friend on wechat, where the student expressed her desire to stay in the U.S. This is evidence of immigrant intent! And you are not "allowed" to have it when you are in the U.S. with a nonimmigrant visa.
Many people tell us they think they are here legally on a tourist visa because it is "good for ten years." But the expiration date on your visa is not the maximum length of your trip to the U.S. You can only stay a maximum of six months without a granted extension.