Orginally started off as a typo for "the", but recently has changed a bit in meaning. "Teh" still means "the", however, it is mostly used in the same manner that spanish speaking people use the word "El".

(addendum)
Has the ability to turn nearly any word into a noun.

Either a typo of the word "The" or a way to show extra emphasis onto the next word.

An expression used by idiots to helpfully identify themselves to other idiots.

1) Typo for "the".
2) Very
3) An Asian name spellchecked with Microsoft Word.

Originally just a misspelling from people typing too fast, "teh" has become a word used by net.writers to exemplify people who are ignorant or simply not thinking clearly (perhaps because they're typing too fast).

Deliberate typo error of "The". used in online gaming discussion