Typically, an infraction is a violation of a rule or local ordinance or regulation.
Some refer to an infraction as quasi-criminal, because conviction for an infraction is generally not associated with the loss of liberty, and are often considered civil cases. Nonetheless, most infractions are indeed violations of statutory law, but in differing with criminal law where the burden of proof is Beyond a Reasonable Doubt, the standard for the civil infraction is a Preponderance of Evidence.
Examples of infractions include jaywalking, littering, violations of municipal codes (such as building or housing), disturbing the peace, or falsification of information. In many jurisdictions today, minor traffic violations have been decriminalized and classified as infractions. For example, in Kern County, California (a county in which Interstate 5 crosses its western edge), large numbers of speeders are ticketed every year while travelling between the Los Angeles Area and the San Francisco Bay Area for excess of 100mph. This is generally considered an infraction resulting in only a fine. In the state of Oregon, possession of less than one ounce of cannabis (marijuana) is an infraction rather than a crime.
Nowadays, many jurisdictions allow first time offenses for minor misdemeanors including trespassing, petty theft, disorderly conduct, and marijuana possession to be reduced to infractions, or municipal ordinance violations, allowing the defendant to avoid having a criminal record which would otherwise jeopardize his long term prospects. This is particularly true if the defendant received only a citation instead of being arrested. However, by allowing a first time misdemeanor offense to be reduced to an infraction, this could also serve as an aggravating factor if the person were to be caught committing another crime.