What happens when using find my iphone app?

What happens to the phone you lost when you use the iphone app find my iphone? Does anything come up on the screen or does a sound happen? I just want to know because if I use it, I don't want the thief to know that I know where they are.

Used it with my iPhone4 lost last year. You have options on what to do (message, sound, erase data). You can only reach your lost phone when it is connected to internet, either on Wi-Fi or cellular.
you will receive an email that your message has been viewed by the other person.

try it if you have two gadgets on you.

It depends on what you do with the options you have available.

You could wipe the data from the phone, have it make a sound even if it is on silent mode, or put it in lost mode, that it would lock down & can be access by someone (you) that has the proper credentials/Apple ID.

Assuming you are running iOS 7 if the person was to try to restore it they would still that in order to go ahead.

Nothing will show on the screen unless you want it to. There are options to send a message, show an alert or play a tone whilst you find your phone. If you are just looking to track it, consider teh Find My Friends application instead.

You can use the Find my iPhone feature to see the location of the phone without anything being visible on the phone itself.

There's an option to play a sound without putting it in lost mode. If you do that, the hone will start making noise and say "Find my iPhone alert" on it.

I'm not sure what you can do with the optional lost mode. And then you can also erase the phone.