What is money transfer operators?

Could you please explain what money transfer operators are? I've heard the term mentioned but am not entirely clear on its meaning. Are they businesses that facilitate the transfer of money from one person or entity to another? If so, how do they operate and what services do they typically provide? Is there a specific technology or system they use to ensure the safe and efficient transfer of funds? Additionally, are there any regulations or standards that these operators need to comply with? Thank you for clarifying this concept for me.