title: How does EC2‘s public ip works?
body: <p>When I launch an EC2 instance,I will get a private ip and public ip.The public ip can be 
  visited by a dns domain like <strong>'ec2-184-73-237-10.compute-1.amazonaws.com'</strong>.When I ping it,I got ip address <strong>184.73.237.10</strong>.</p>
  
  <p>My question is: does 184.73.237.10 only belongs to me or it's shared by different instances? 
  If it's shared by different instances,how does it work? As far as I know, each instances(linux) can be accessed by ssh.</p>
  
  <p>Thanks in advance :-)</p>