arduino + microphone

I am working on a project in which, I have to interface arduino with microphone. I want to enable (turn ON) the microphone for the speaker from a webpage button. I know how to control a webpage using ethernet shield and I am done with that part, I just want to know that which microphone is applicable to interface with arduino and what is the pin configuration of it.

Is this a PA system or something?

You can switch the microphone on/off with a relay. Don't try sending the signal through the Arduino because the Arduino has no true-analog outputs.

can we use the analog pins of arduino ?. And also whats the exact name of the microphone module we can use ?

This is simply a class room or a conference room scenario in which the operator will allow the student to speak and turns on his microphone, whereas the source of communication is arduino (through ethernet shield) and webpage interface.