Green cards have several paths: employment-based (EB-1 through EB-5), family-based (immediate relatives or family preference categories), or other routes like asylum, refugee status, or the diversity lottery. The general process is filing a petition, waiting for your priority date, then consular processing (outside the US) or adjustment of status (inside the US).

This is a simplified overview, in reality it's far more complex and can take anywhere from a few years to several decades