It's primarily used as a conjunction, which connects words, phrases, or clauses. For example:
* "I wanted to go to the party, though I was tired."
It can also be used as an adverb, meaning "however" or "nevertheless." For example:
* "The weather was bad, though we still had a good time."
There are rare instances where "though" might be used as a noun, but those cases are very specific and usually involve referring to the word itself.