These are my photos from parks I have visited (I didn't take them, they are all from Wikimedia Commons).
This shows you how to make a simple image gallery using articles in com_content.
In each article put a thumbnail image before a "readmore" and the full size image after it. Set the article to Show Intro Text: Hide.
Modules are small blocks of content that can be displayed in positions on a web page. The menus on this site are displayed in modules. The core of Joomla! includes 24 separate modules ranging from login to search to random images. Each module has a name that starts mod_ but when it displays it has a title. In the descriptions in this section, the titles are the same as the names.