diffExplanationTable

<table border="1" width = "50%">
        <tr >
          <th>character</th>
          <th>meaning</th>
        </tr>
        <tr >
          <td align="center"><b>!</b></td>
          <td>Indicates that this line is part of a group of one or more lines that needs to change. There is a corresponding group of lines prefixed with "<b>!</b>" in the other file's context as well.</td>
        </tr>
        <tr >
          <td align="center"><b>+</b></td>
          <td>Indicates a line in the answer file that needs to be added to your file.</td>
        </tr>
        <tr >
          <td align="center"><b>-</b></td>
          <td>Indicates a line in your file that needs to be deleted.</td>
        </tr>
</table>