“That's all, folks!”
Often mistaken for this, it, the thing and the doohickey, that has been in existence since 50,000 years before the conception of God - i.e. forever. If that is somehow too hard for you to understand, why don't you just take a look at this instead. That is a mysterious, omnipresent substance which is in every item ranging from the humble bumblebee to the bumblebees who constantly brag about how awesome they are. The most common that-to-other-stuff ratio is pi-to-one. Items and phenomenon which defy description have long been described as being "all that." Despite this, many uninformed people insist on "having none of that."
What 'That' is not
That's not a knife. That's a knife!
That that that that that
This and that have been lumped together by humans for millenia. However, keep in mind that you cannot "Smack This," say, "This's hot," or talk about "All This Jazz," because that would make you a n00b. This and that started out as bitter enemies, engaging in great and terrible wars (great due to the special effects, and terrible because they lasted as long as the typical Dragonball Z fight). Over time, that and this became rivals, and, with the emergence of humanity, begrudgingly work together to prevent humans from noun overload. That is most commonly seen as a noun in reference to one's engorged yet flaccid penis, consisting of more than 6 trillion microscopic boners sprouting from the tip.