"A truly beautiful, riverfront community in Summerville, South Carolina."
Some communities hold gender-specific events (e.g., "men's golf outing" or "ladies' night out") and like to be able to send communications about those events to just the residents who would be interested.
If your community opts to send these types of communications, providing your gender will help ensure you only receive relevant emails, texts, etc.
If you choose not to provide your gender, you'll simply receive emails sent to both genders. That way, you won't miss anything important.