For many people, there is no distinction between the use of "which" and "that" as relative pronouns, but good writing does draw a line between them. "Which" should be used for parenthetical phrases and "that" for non-parenthetical. For example, "the south side of the house, which was exposed to the sun, is blistered and faded". The house has only one southern side, so the phrase "which was exposed to the sun" is incidental to our understanding and could be omitted. To rephrase the sentence, if it read "the side of the house that was exposed to the sun is blistered and faded", then the information is needed and the word "that" is used as a relative pronoun.

hi "which" usually use instead of object but "that" is useful for everyrole!