The guy that said DUI and DWI are the same is wrong.
First, states have different blood alcohol levels that qualify as intoxicated.
Second, assume you are driving funny on a Friday night and a cop pulls you over. They will test your blood alcohol level using breathalyzer. If it shows you have been drinking but your blood alcohol levels is below the legal intoxication level, then that is a DUI, and it is a lesser offense.
Last I heard, some states like Texas don’t even have such a thing as DUI. It used be and still might be, that if you are not intoxicated then the cops will force you to get a ride home but there is no criminal charge.
DWI means you were caught driving with a blood alcohol level that is above the legal intoxication limit. In most states, the legal intoxication level is so high that if you actually go over it then you are certainly very obviously drunk. This is a much more serious charge.