bu - this
şu - that (pointing at an object that can be seen)
o - that (indicating an object that can not be seen)
As in English, these indicatives can be used as adjectives or as pronouns.
bu elma - this apple
şu ağaç - that tree
o ev - that house
Recall that there is no word for "is" in the Turkish language. Therefore, when using indicatives to say "this is an apple", simply say, "bu bir elma". More examples:
Bu benim arkadaşım. - This is my friend.
Bu ne? - What's this?
Bu bir kalem. - This is a pen.