A clothing optional beach is a beach where people are allowed to be nude. At official clothing optional beaches, it's legal for people to be nude. At unofficial clothing optional beaches, it's illegal for people to be nude, but law enforcement doesn't interfere.
Although the terms "clothing optional" and "nude" are sometimes used interchangeably, nude beaches sometimes require people to be nude, whereas clothing optional beaches simply allow nudity. Clothing optional beaches tend to be located away from areas frequented by the general public, and they usually have limited facilities.
Clothing optional resorts, which are entire resorts where people are allowed to be nude, sometimes include beaches. However, since the beach is usually public land, it's not always legal to be nude at these beaches, even if they're by the resort. The beaches at clothing optional resorts typically have more facilities than other clothing optional beaches.
Official clothing optional beaches typically have signs warning beach goers that nudity is allowed. In some cases, clothing optional beaches are adjacent to beaches that require clothing. Clothing optional beaches usually have rules against sexual harassment and sexual activities.
One variation on clothing optional beaches is topless beaches. These beaches allow women to go topless, but they must still wear clothing that covers the groin area.