What do boys mean by hee hee?

Express a relaxed, happy and happy mood.

This is a modal particle or onomatopoeic word, which is used to express laughter or pleasant feeling in spoken language. A boy uses "hee hee" to show that he is interested in something, funny, or wants to convey positive emotions when communicating with you. It can be used to respond to a humorous incident, an interesting topic, or simply to show that he likes the current conversation.