Calling codes are numerical prefixes used to identify specific countries or regions when making international phone calls. Each country is assigned a unique code, which must be dialed before the local phone number. For example, the calling code for the United States is +1, while India has the code +91. These codes help telephone networks route calls correctly across borders. When dialing internationally, the caller typically starts with a "+" sign or "00," followed by the country code and then the local number. This system ensures that calls reach their intended destinations efficiently.