title: What is the difference between the Point and Vector3 geometry message if they're exactly the same?
body: <p>I'm pretty new to ROS but I was manipulating a custom message that was made up of <code>geometry_msgs/Point</code> and <code>geometry_msgs/Vector3</code> messages. When I printed out the message I noticed that both the <code>Point</code> and the <code>Vector3</code> had the same 3 attributes (<code>x</code>, <code>y</code>, and <code>z</code>) and this made me curious because it seemed redundant... right? </p>
  
  <p>Upon further digging in the source code, it turns out the <code>Point</code> and the <code>Vector3</code> are exactly the same. They're both composed of a <code>float x</code>, <code>float y</code>, and a <code>float z</code>. </p>
  
  <p>But after reading the <a href="http://docs.ros.org/jade/api/geometry_msgs/html/msg/Vector3.html" rel="nofollow noreferrer">docs</a>, it seems like there IS a difference between these two messages. The docs mention that a Point should be used if the user wants to apply a translation whereas a Vector3 should be used to only represent a direction (and magnitude I guess?).</p>
  
  <p>Since the two messages are defined exactly the same, I reckon if I could apply a translation to a <code>Point</code> I could also apply a translation to the <code>Vector3</code>. Is there a difference I'm not seeing between the <code>Point</code> and <code>Vector3</code> that isn't their name?</p>