title: what is the difference between properties and patternProperties in json schema?
body: <p>For the following json string : </p>
  
  <pre><code>{
      "abc" : 123,
      "def" : 345
  }
  </code></pre>
  
  <p>The following schema considers it valid :</p>
  
  <pre><code>{
      "$schema": "http://json-schema.org/draft-03/schema#",
      "title": "My Schema",
      "description": "Blah",
      "type": "object",
      "patternProperties": {
          ".+": {
              "type": "number"
          }
      }
  }
  </code></pre>
  
  <p>However, changing the the patternProperties to properties still considers it valid. What then, is the difference between these 2 tags?</p>