What's different between " somebody" and "someone"?

I think It's a little bit different, but I have no idea to find it out. 

why many person here dont reply message?

I sent lot of message to someone and want to help them in Mandarin or Cantonese, or to be languages partner.

why them dont reply me? 

What's different between "werid" and "wierd" ? I'm confuse about that..