That Old Which Has Me Confused

I'm always confused about when to use which or that. Wondering Which.

In American English, there is a difference between "which" and "that."

"Which" is non-restrictive; in other words, it introduces parenthetical, or non-essential, information to a sentence.

Your etchings, which are on the coffee table, are exceptional.

This means, all the etchings in the room are exceptional; oh, and by the way, they're on the coffee table. Notice the commas around the nonrestrictive phrase.

"That" is restrictive, or essential, to a full understanding of the sentence.

The etchings that are on the coffee table are exceptional.

This means there are other etchings on other tables in the room, but the only exceptional ones are on the coffee table. Notice, there are no commas.

I hope your question, which was a good one, is clarified.