When you petition relatives oversea, you only file I130 with USCIS. After ther I130 is approved by USCIS, your case will then forwarded to NVC (national visa center) for immigration visa processing with the embassy at your relatives' country of residence. Immigration visa processing at NVC is a multi-step process. More information can be found at the http://travel.state.gov/visa/immigrants/info/info_1335.html