Unless a foreign national is an immediate relative of a U.S. citizen, there will be a "wait period" before an application for U.S. permanent residence can be filed. This graphic summarizes the various wait periods, which can be as long as 23 years for some people. Immigration lawyers can help people to select the fastest wait period, which can be complicated.
Visa Bulletin as of January 2019
Approximate wait periods calculated using information available at https://travel.state.gov/content/travel/en/legal/visa-law0/visa-bulletin/2019/visa-bulletin-for-january-2019.html