|He's having his hair cut|
Image: 'Raphael in action'
If we analyze the previous sentence, we find the structure have + object + past participle, or to put it more nicely: have something done.
Let's see another example: Your car is broken and you take it to the garage to...
a) repair it
b) have it repaired
If you chose the second option you are right, because I suppose you wanted a mechanic to repair your car and not do it yourself!
|A mechanic at work|
Instead of using the verb have, you can also use get if you want the sentence to sound more colloquial. Besides, get is preferred in the imperative form: “Go and get your hair cut, you look like a hippy”.
Image: 'Keeping it Real, West Jerusalem'
This structure can also be used in cases in which nobody is asked to do the action: “ He had all his money stolen while he was on holiday” (He didn't ask anybody to steal his money, it just happened), and even to say that something disagreable happened to someone: “We got our house flooded last night”.
The verbs have and get in this structure can be found in all the tenses.
You will find some more examples in this presentation: