Form I-130 is the immigrant petition that must be filed by a US citizen or a permanent resident, to sponsor a family member for a US Green Card. US citizens can sponsor a few other categories of relatives apart from their immediate relatives, whereas Green Card holders can only sponsor their spouses and their children. After you file Form I-130, in the United States, your petition will be forwarded to the National Visa Center for processing, after it is approved by the USCIS. National Visa Center (NVC) will review the affidavit of support forms filed by you and collect the required fee. Similarly, it will provide instructions and collect the other required documents. Immediate relatives are not subject to numerical limits and they will not be required to wait until the priority dates become current and their petitions will be processed sooner. But, if Form I-130 is filed on behalf of other relatives, NVC will contact the beneficiaries only after visa numbers become current and the process will be quite lengthy.
After Form I-130 is sent to the NVC, the visa center will inform the beneficiary about the visa application fees and then the beneficiary must collect her visa application and the required supporting documents. She must then wait until the NVC schedules an interview at a local US Embassy or Consulate and the NVC will notify the beneficiary only if the priority date meets the Qualifying Sate and she can check the visa bulletin for information about the priority dates and the Qualifying Dates will be updated every month by the DHS. Remember that a priority date will be assigned as soon as you file Form I-130 and you can find that date on the USCIS Approval Notice, that was sent to you.
NVC will schedule visa interviews and send all the forms that were submitted, on behalf of the beneficiary, to the respective US Consulates or Embassies, where the beneficiary will be interviewed. And the beneficiary can start preparing for the interview after receiving a notification from the NVC. After the approval of Form I-130, your family member will be called for an immigrant visa interview sooner, if the petition gets through the NVC quickly. At times, an interview will be scheduled, within one month from the date of approval of Form I-130 and at times, it might take more than 6 months. This depends on the category and immediate relatives of US citizens, may not be required to wait for a long time and an interview will be scheduled sooner, but the beneficiaries who are not immediate relatives will have to wait for years. However, you may check the visa bulletin that the DHS publishes every month for information on priority dates and qualifying dates.