H1Bs usually require the employer to prove they couldn't find someone within the country.
Temporary work visa: H-1B, H-1B1, or E-3
"The employer needs to demonstrate that the worker is being paid at least the prevailing wage for that region and occupation, and comparable to native workers in the firm, and that employing the worker will not adversely affect current workers. The employer does not need to demonstrate that there is no qualified native U.S. worker for the job."
Compare that to:
Employment-based visa (such as EB-2 visa, or EB-3 visa) that provides a path to permanent residency (a Green Card)
"The employer needs to demonstrate that there is no qualified U.S. worker willing to do the job at a comparable wage, and needs to have made a good-faith effort to recruit a native U.S. worker."
You only need to demonstrate an effort to recruit someone when applying for a green card.
EDIT: ok, maybe my immigration lawyer was a weirdo :)
The actual wage: This is the wage paid to other employees in the company who do the same work.
The prevailing wage: This is the wage for that occupation in the geographical area.
See: https://en.wikipedia.org/wiki/Labor_Condition_Application##1... https://en.wikipedia.org/wiki/H-1B_visa#Labor_Condition_Appl...
No, this is only part of employment-based greencard (LC) process. For H-1Bs, as part of the LCA process, the employer needs to advertise that a candidate is going to be hired.