I am a complete noob to arduino and need some advice

So I am looking to make a wireless motion sensor for fun. I have found plenty of guide online on how to make one, however first I need to choose a Arduino board. I found this one http://www.gearbest.com/development-boards/pp_62975.html?currency=USD&gclid=CIvL5MC27MMCFcOGaQod-KQAxg and it is only $6, and that seems a little cheap to me. Would that board work for my needs? Also is there any way to get an arduino to transmit a signal to either a wireless earpiece or my headset on my computer, maybe a beeping noise? Thank you all very much :D

Sounds about right for a cheap Uno knockoff. Pro Mini and Nano knockoffs get as low as $3-4. Most of the clones work fine, but sometimes they don't have a working bootloader pre-programmed (and you cannot bootload an arduino without another working arduino or an ISP like the USB Asp)

Note that it is NOT the same as a "real" Uno - that one uses the CH340G serial interface. The real Uno uses an ATMega16u2 to act as a serial interface - but it can also be reprogrammed to impersonate a keyboard or mouse, or do other cool things (though these are advanced features).

As for the wireless earpiece... There are many ways to get a message to a connected computer, and then a program on the computer could be written to look for that and react appropriately. That's one way. I am not sure if there are things that you can pipe audio to which will turn it into a wireless signal that could be received by a headset, though I suspect those exist. In that case, you could use tone() and it'd be real easy. Or you could just use tone() to drive a speaker, or even use a DC buzzer if you don't care about it going to a headset - that'd be way easier.