It is used to show laughter online.

Thank you for asking this question my fellow landscape designer. It is a change in level that is concealed from view to create a barrier without requiring a fence to keep livestock in or out depending on the context. This was used to great effect in English Landscape Design of the 18th and 19th Centuries. Great question.

Ha ha can mean many things depending on the context. It can be a sarcastic comment, it can just mean something is funny, it can differ depending on the region it is said in. For example. You say to be I look like a frog. I say, "haha, very funny." I am being sarcastic. Say we both see a mouse on a frogs back during a flood. We both laugh, Haha! because it really is funny. It can be used for ahha on rare occasions. Say if Sherlock Holmes discovers Dr. Moriarty's hiding place he may say, "Haha, I have caught the scoundrel at last!"

haha = mother in Japanese

Whenever I want to scare my 3 years old cousin I say ha ha ha. she runs and does not disturb me all the day. That's what ha ha mean to me. :D