Let’s make them into full sentences: This is an amazing picture. That is an amazing picture. Now, in Grammar Monster, there is an introduction to 'this/that'. Read the information there, and let me know. www.grammar-monster.com/glossary/demonstrative_pronoun.htm
got it .. thanks .. can we say "its an amazing picture" ?
When we say, "its an amazing picture", we have used a contraction of 'it is', We show that by writing: it's an amazing picture Notice that " it's " has an apostrophe. " its " is what we use - just like, 'his, her" - to show possession: The dog was wagging its tail. There is more about this on Grammar Monster at : apostrophe