By itself, the filing of a visa petition on Form I-130 does not give an intending immigrant any lawful status within the United States. What it does achieve depends on the family relationship and where the immigration currently is.
The I-130 is a Petition for Alien Relative, meant for use by U.S. citizens and lawful residents to bring family members into the U.S. as lawful permanent residents (green card holders). The I-130 is meant to legally establish the relationship between the petitioner (U.S. citizen or resident) and the person(s) wishing to enter the United States. The form may be filed out for a citizen's spouse, children (married or unmarried), parents, and siblings; or a permanent resident’s spouse or child (unmarried).
Once the petitioner's status and the familial relationship are established, the I-130 will likely be approved by U.S. Citizenship and Immigration Services (USCIS). Many people make the mistake of thinking that this approval is the last step in the process and that the incoming relative is now considered a lawful U.S. resident. In fact, the I-130 is merely the first step in a process. There is still a chance that problems can pop up.
If the intending immigrant lives overseas, then approval of the I-130 will result in the application being transferred to the National Visa Center for further processing.
It may actually stay here for years, if the applicant is in a preference category of visa-eligible people. What's a preference category? It's a visa type that is subject to annual limits on the number of visas granted. Inevitably, more people apply for immigrant visas every year than the legal limit on how many can be given out. So, long waiting lists have developed -- often from five to 25 years, depending on category and country (there are also per-country limits). The waiting list is managed by the person's "priority date," or the date upon which the I-130 was first filed.
Some relatives are considered "immediate relatives," and do not face this added wait for a visa. Immediate relatives include a U.S. citizen's spouse, parents, and unmarried children under the age of 21. Everyone else is in one of the preference categories.
Only after the person's priority date (if any) has become current and a visa is available will the NVC transfer the case to the appropriate U.S. consulate. The immigrant applicant will receive further instructions and have to attend an interview before receiving a visa to come to the United States. He or she will also have to show that none of the grounds of inadmissibility block his or her eligibility for a green card.
For immigrants who are living in the U.S. when their I-130 is approved, its significance is especially confusing -- and especially important to understand. First off, let's repeat that an I-130 gives the person no rights to remain in the United States. If you have a valid status (for example, a student, visitor, or other visa), you can remain until your permitted stay under that status ends. But in any other circumstance, staying in the U.S. unlawfully while awaiting your green card is likely to result in that green card being denied rather than granted. See Must You Leave The U.S. to Wait For Your Green Card?
The issue is that U.S. immigration law penalizes people who stay in the U.S. unlawfully. Those who remain unlawfully for six months or more and then leave voluntarily will face a three-year bar on returning. Those who remain unlawfully for a year or more and then leave voluntarily face a ten-year bar on returning. Those who are deported (removed) from the U.S. may face an even longer bar on returning, depending on the reason for their removal. The bottom line is that the U.S. immigration authorities want people to wait for an immigrant visa OUTSIDE the United States.
Notable exceptions exist, however. For example, immediate relatives of U.S. citizens can actually file their I-130 along with an application for adjustment of status, upon which their U.S. stay becomes lawful. They will be given a work permit while they await their green card interview.
And certain other people may also be eligible to adjust status in the U.S. -- meaning they wouldn't have to leave for a consular interview, and therefore wouldn't face any bar on returning.
As you are no doubt noticing, this is a highly complex area of immigration law. Any questions about your own case, in particular your eligibility to adjust status, and whether you would face a time bar if you applied for your green card via a U.S. consulate, should be directed to an experienced U.S. immigration attorney.