これ/それ/あれ are used as the subject of a sentence. この/その/あの are used to modify a noun. この/その/あの are used on their own, without any particles. これ/それ/あれ are generally used with particles. Example: これは面白い本です。 この本は面白いです。 So in the first sentence これ is the subject, but in the second sentence 本 is the subject and この is a pronoun used for emphasis.

この/その/あの - are demonstrative determiners. Thus, they affect the noun the are referred to. これ/それ/あれ - are demonstrative pronouns (derived from the above). -この /kono/ + noun "this *"→ indicates an object that is near the speaker. ex. この犬 = "this dog (over here)" これ [pronominal function] "this one" → indicates an object, action, topic, that has been mentioned before or is to a degree already known by/near the speaker. ex. これが欲しい = "I want this one (here)" ここ [adverbial function] "here (near me)" ex. ここへ来て "come here" (informal) -その /sono/ + noun "that *" → indicates an object that is near the listener . ex. その犬 = "that dog (over there)" それ [pronominal function] "that one" → indicates an object, action, topic, that has been mentioned before or is to a degree already known by/near the listener. ex. それが欲しい = "I want that one (near you)" そこ [adverbial function] "there (near yourself)" ex そこへ行く = "I come there" (informal) -あの /ano/ + noun "yon *" → indicates an object that is distant from both the speaker and the listener . ex. あの犬 = "yon dog (yonder)/ that dog (distant from both of us in terms of space/time)" あれ [pronominal function] "yon" → indicates an object, action, topic, that has been mentioned before or is to a degree already known by/distant from both the speaker and the listener. ex. あれが欲しい = "I want yon one (distant from us)" あすこ [adverbial function] "yonder" ex. あすこへ行こう = "let´s go yonder" (informal)

Also, there is a formal construction which uses the same system of the above: *こちら-(particle) = formal construction, litterally meaning "this way" → a.こちらの [determiner] ex. こちらの犬. = "this dog over here" b. こちら+partilcle [pronoun] ex. こちらが欲しいです = "I would like this one over here" c. こちらへ [adverb] ex. こちらへ来てください = "please come over here" *そちら-(particle) = formal construction, litterally meaning "this way" →  a. そちらの [determiner] ex. そちらの犬. = "that dog over there" b. そちらの+partilcle [pronoun] ex. そちらが欲しいです = "I would like that one over there" c. そちらへ [adverb] ex. そちらへ行きます = "I go over there" *あちら-(particle) = formal construction, litterally meaning "this way" →  a. あちらの [determiner] ex. あちらの犬. = "yon dog (yonder)" b. あちら+partilcle [pronoun] ex. あちらが欲しいです = "I would like yon one (yonder)" c. あちらへ [adverb] ex. あちらへ行きましょう = "let us go yonder"