The Wanted Level system in Vice City dictates the intensity of police pursuit. Stars on the top-right of your screen indicate your wanted level, ranging from one (minor offense) to six (military intervention). Committing crimes like speeding, hitting pedestrians, or engaging in shootouts will increase your wanted level. To reduce your wanted level, you can lay low, find a Pay 'n' Spray (to change your vehicle's color), collect police bribes (star icons), or complete certain missions.
At higher wanted levels, the police become more aggressive, deploying roadblocks, spike strips, and even helicopters. Understanding how to evade the police is a vital skill. Often, a fast car and knowledge of the city's shortcuts are your best defense. Remember, the military at six stars is nearly impossible to escape, so try to avoid reaching that level unless you're feeling particularly suicidal.