Use that to introduce a restrictive clause, which is a clause that is essential to the meaning of the sentence. Use which to introduce a nonrestrictive clause, which is a clause that you can omit without affecting the meaning of the sentence. If you can insert a comma before the clause, it is nonrestrictive.
Examples |
The red dot indicates that you have new voicemail messages. |
The available permissions are based on the company policy, which your company administrator sets. |
