this 这，这个，后跟单数名词，比如这本书，this book.
these 这，这些，后跟复数名词，比如这些书，these books.
those 那，那些，后跟复数名次，比如那些书，those books.
而且，these一般指较近的一些人或事物，而those指较远的一些人或事物
1.作主语、宾语、
表语或定语。
This is my book. 这是我的书。
Do you like this? 你喜欢这个吗？
That book is mine. 那本书是我的。
What I want is this? 我要的就是这个。
2. this / these一般用来指时间或空间上较近的人或物；而that / those常指时间或空间上较远的人或物。
This is a pen and that is a pencil.
We are very busy these days.
3. this / these可指后面要讲到的事情，而that / those常指前面提到过的事物。
John asked me to help him with his lessons this evening. I’m afraid I can’t do that.(that指上句提到的help him with his lessons)
4. that / those可用来指代前面提到的名词。
This book is not so interesting as that I read yesterday.
这本书不如我昨天看过的那本有趣。(that指代the book)
5. 在打电话时，常用that询问对方是“谁”，用this介绍自己是“谁”。
—Is that Mrs Black speaking ? 你是布莱克夫人吗？
—Yes, Who’s that ? 是的，你是哪一位？
—This is Mary, Mrs Black.我是玛丽，夫人。