What is bitcoin OTC trading?

Could you please explain to me what bitcoin OTC trading actually means? I've heard about it but am not quite sure how it differs from regular trading. Is it more secure? Are there any specific advantages or disadvantages to OTC trading bitcoin compared to traditional exchanges? Could you also clarify how the transactions are typically executed and whether there are any regulatory considerations that need to be taken into account? Thank you for your assistance in helping me understand this topic better.