What is humour

I am half half about our class book for  this part of the term. I am not one of the deep belly laughers but do have the odd chuckle here and there. I have missed some parts of the book though I can still get the idea. What is humour I believe humour is something that makes people laugh but is also brightens the mood, or if someone is felling sad or down and joke or something funny can make them fell better. That is what i believe humour is.