Job Offer/Work Related Immigration
Because of the long waiting times for an Immigrant Visa (Green Card) most foreign workers start working in the US on a Non-Immigrant Visa, H-1B or O-1.
Another option is relocation through an international employer also based in the US (L-1A and L-1B).
Different requirements apply to each of these visas. Non-Immigrant Visas allow for a limited stay in the US only.
H, O and L are “dual intent” visas making possible to temporarily work in the US with the intention to immigrate permanently.
For permanent immigration in most cases the employer must file the petition for the foreign worker.
It is also possible to begin a new business or buy an existing business in the US and work in it, through an E-2 Visa. This is a Non-Immigrant Visa that can be extended as often as needed. However it does not give the option to apply for a Green Card.
Employer Sponsored Immigration is divided in several categories called Preferences. For each category a limited number of visas is available. Together with the per country-limit this means (long) waiting times.