The letter het represents trascendence, divine grace and life.
Some letters are very similar to each other in their pronounciation and, under certain conditions, can be interchanged. That is the case of het and he, both belonging to the same group of guttural numbers.
At Passover, it is mandatory to eat matza, azyme, and it is forbidden to eat hametz, leavened product.
All the letters in matza and hametz are identical, except for het and he.
The difference between the letters of the two words is a tiny space on the left leg, the same space that marks the difference between a het from a he. The minuscole difference indicates that lack of precision in preparing and cooking the matza turns it into hametz. (source: Alshich)
In chat rooms, online forums, and social networking the letter het repeated denotes laughter, just as in english, in the saying 'haha'.
The letter shape ultimately goes back to a hieroglyph for "courtyard", named hasir in the bronze age alphabets. The hebrew word for courtyard is hatzer.
You can see below the movie of me doing a hebrew letter in clay, the prototype for a jewel.