We use the determiner 'this' (pl. 'these') when we speak about people, things or events that are present at the moment or near in time.

• This book is a best seller.
• Is this your car?
• Early this morning.
• These postcards are from Holland.
• I like these shoes.

We use the determiner 'that' (pl. 'those') when we speak about people, things or events that aren't near or present at the moment.

• Do you want that pair of shoes?
• That man is a doctor.
• Those children are very polite.
• Look at those clouds!
• How much are those apples?