Why my local image is only found when using bloginfo('template directory')

Try using the get_template_directory_uri() function.

<img id="about" src="<?php echo get_template_directory_uri(); ?>/images/about.jpg" alt="about" />

https://developer.www.ads-software.com/reference/functions/get_template_directory_uri/

I did manage to get it working I’m just trying to understand why it won’t work by just saying:

<img id=”about” src=”/images/about.jpg” alt=”about”>

Why can’t wordpress find it without using php?

It could, but it is not relative to the php-file. So the relative url would be something like:
<img id=”about” src=”/wp-content/themes/Your-Theme/images/about.jpg” alt=”about”>/

Thanks! That almost worked, I had to go back one more directory but it worked so now I know where it is searching from ??