DIRECT QUESTION: What time is it?

INDIRECT QUESTION: Do you know what time it is? 

We use indirect questions when we are trying to be more polite (example: asking for help in the street).
Excuse me do you know if there is a supermarket near here?
In indirect questions we don't use inversion (changing the word order)


The bank is near the supermarket.
D: Is the bank near the supermarket?
I: Do you know if the bank is near the supermarket?


Don't use auxiliary verb. 
I'd like to know if you want to come with us? 

For yes/no questions we use if of whether

Do you know if she is able to help me with my homework?

Common phrases

I'd like to know where you bought that lovely floral dress?
Do you know if it's going to rain?
Can you tell me where the train station is?
Could you tell me whether this car is for sale?

Change the direct questions into indirect questions. Use 'can you tell me'.

1) Where does she play tennis?
2) Does he live in Paris?
3) Is she hungry?  
4) What is this? 
5) Do they work in Canada? 

Change the direct questions into indirect questions. Use ‘could you tell me’.

1) Can she swim?
2) When can they come?
3) Why must she leave?
4) Must he cook tonight?
5)Why should I leave early?

Further reference:

Gold coursebook page 124; Grammar reference; 1.5 Indirect questions
WEB: Perfect English Grammar; Indirect questions 
(contains examples and exercises) 
VIDEO: BBC Learning English; Six minute grammar - Indirect questions