causative verbs "let," "make," "have," and "get."

[let + person + verb]
This construction means "to allow someone to do something."
John let me drive his new car.


[make + person + verb]
This construction means "to force someone to do something."
My teacher made me apologize for what I had said.


[have + person + verb]
This construction means "to give someone the responsibility to do something."
Dr. Smith had his nurse take the patient's temperature.


[get + person + to + verb]
This construction usually means "to convince to do something" or "to trick someone into doing something."
Susie got her son to take the medicine even though it tasted terrible.


Get vs. Have
Sometimes "get someone to do something" is interchangeable with "have someone do something," but these expressions do not mean exactly the same thing.


Reference:
http://www.englishpage.com/minitutorials/let.html

• Have

Have + object + verb 3 (past participle) - have something done
Have + object + infinitive -- have someone do something

We use causative when arranging for someone to do something for us
They had their car repaired. (They arranged for someone to repair it)
Compare: They repaired their car. (They did it themselves

We use causative when someone does something to us.
Bill had his money stolen

We can use have someone do something to talk about giving instructions or orders (more common in American English).
I had my assistant type the report.
I'll have my lawyer look into it.


Get is possible instead of have, usually in informal spoken English.
I'm going to get my car fixed tomorrow.


http://www.eslbase.com/grammar/causative