Sometimes people laugh when they are not happy. When people are ashamed or embarrassed, sometimes they react by laughing.
There are different ways to laugh. A person can laugh using mostly their voice, mostly their throat, or mostly their nose.
You can write a laugh in different ways. Some people write "ha ha ha", or "he he he", or "hehe". If they are on the internet, they also use "LOL". "LOL" does not sound like a laugh, but it stands for Laughing Out Loud.
Laughter can be observed in human babies from around three or four months and is usually an expression of surprise. Babies' laughter often produces a positive response in adults who will involuntarily copy the child. Video footage, on the YouTube site, of babies laughing was shown to Queen Elizabeth II during her visit, on 16 October 2008, to the Google headquarters, where both she and her husband the Duke of Edinburgh were reduced to 'fits of giggles'.