Homophones are words that sound alike but have different spellings and meanings. Here's the breakdown for "then" and "than":
Then: Used to indicate sequence or time (First, we eat. Then, we play).
Can also mean in that case (If it's raining, then I'll bring an umbrella).
Than:Used in comparisons (This apple is sweeter than that one).
There, their, they're: As you already covered, "there" refers to a place, "their" is a possessive pronoun, and "they're" is a contraction of "they are."
Two, too, to: "Two" is a number, "too" means "also" or "excessively," and "to" is a preposition indicating direction or purpose.
Your, you're: "Your" is a possessive pronoun, and "you're" is a contraction of "you are."
Its, it's: "Its" is a possessive pronoun for singular nouns that don't end in "s," and "it's" is a contraction of "it is."
Hear, here: "Hear" is a verb meaning to perceive sound, and "here" refers to a location.
Peace, piece: "Peace" is a state of tranquility, and "piece" is a part of something.
Whole, hole: "Whole" means complete, and "hole" is an opening in something.
Know, no: "Know" is a verb meaning to have knowledge, and "no" is a negative answer.
Their, they're, there: (Yes, this one is a triple threat!) We covered these already, but it's a common trouble spot.
Right, write: "Right" can be an adjective meaning correct or an adverb meaning correctly, and "write" is a verb meaning to create written text.