An acquittal in Louisiana results in a dismissal of the charges. Usually, it is used in reference to when a judge or jury finds a defendant not guilty of a crime. This will happen after a trial on the merits is conducted and the trier-of-fact (judge or jury) is asked to return a verdict.
Charges can also be dismissed by the prosecutor. The prosecutor, whether it is the district attorney representing the State or the city prosecutor representing the City, has the power to bring a criminal charge as well as make it go away.