A taxonomy is a way to group content. Categories and tags are the built-in taxonomies. A custom taxonomy lets you create your own groups, like project types, genres or brands,…

WP_Query lets you fetch posts with your own rules, like a specific category, post type or number of items, and display them anywhere in your theme.

Featured images, also called post thumbnails, need theme support first. After that, use has_post_thumbnail() to check if the post has an image and the_post_thumbnail() to print it.