The Dynamic Source function requires a little more context to understand what's going on...
Below you see a grid of Joomla articles in an overview, a click on the button "Show me this example" takes you to the corresponding article page (com_content article).
Each article was assigned a picture folder with the corresponding pictures of this hotel. On the corresponding article page you will find the OrielPro gallery which shows these pictures.
The clue is, it is always the same module / module instance. So you don't have to create galleries for three, four, twelve or several dozens of galleries to display the corresponding images in each article. One module in dynamic mode is sufficient. Using the information in the custom field, OrielPro reads the corresponding image folder and shows you the images directly. This ensures that all galleries are displayed identically on all pages, and if you want to change something in the design you only have to do it in one place.
OrielPro is an extension (module) for the Joomla! CMS.
The Future is here. Oriel Pro gives you the freedom not just to present images in a modern look. With OrielPro, you can create entire album libraries. Adding new albums and images is easy via FTP or file manager. OrielPro automatically detects new content and updates your albums.