This becomes more clear through this example:

As you can see, I built a 2x2 table, which contains an image in every cell. The corresponding HTML code looks like this:

<table>
  <tr>
    <td><img src="https://www.number13.de/content/images/2019/04/Factory-Town.jpg" width="300"></td>
    <td><img src="https://www.number13.de/content/images/2019/03/League-of-Legends.jpg" width="300"></td>
  </tr>
  
  <tr>
    <td><img src="https://www.number13.de/content/images/2019/07/Shakes-and-Fidget.jpg" width="300" ></td>
    <td><img src="https://www.number13.de/content/images/2019/07/Eco.jpg" width="300"></td>
  </tr>
</table>

To add an image, between the brackets <td></td> the following code is needed:

<img src="https://www.number13.de/content/images/2019/04/Factory-Town.jpg">

The link of the image is pasted in between the quotation marks. To make all images in the table equally wide, I added the attribute width="300". Such attributes have to be always added in between the <img> brackets.