Are barter agreements legal?

Could you please clarify for me if barter agreements are considered legal transactions in the eyes of the law? I understand that these agreements involve the direct exchange of goods or services without the use of money, but I'm curious about their legal status. Are there any specific regulations or restrictions that govern how these types of agreements can be structured and enforced? Additionally, are there any potential tax implications that businesses or individuals should be aware of when entering into a barter agreement?