Dig through the WordPress Codex page on Template Tags, looking for functions that might be useful to implementing your gallery.
Use at least three functions you find there in your theme.
Write at least three short paragraphs about the functions you chose, one paragraph for each. Describe what the function does and why you chose to use it in the theme. If you use more than three functions (you probably will), you only need to write paragraphs for three.
This is a pass/fail assignment. In other words, you must do it. If you do, you pass. If you don’t you fail.