Find searches through photos within an active contact sheet tab. You can open the Find window by either navigating to Edit> Find or using the keyboard shortcut command-F (macOS) or control-F (Windows.)
Find searches through both superficial information (the name of a photo) and the IPTC data associated with a photo.
Find: Any of the words/All of the words: If your search phrase has more than one word, specify whether you want to find any word in the phrase or only results that have all the words. This is useful if you want to find only photographs from a single photographer in a shoot (All of the words: Smith Bob) or from two locations (Any of the words: Salem Eugene).
In: Selected items/All items: Choose Selected items if you have already selected photos in your contact sheet and are trying to drill down further. Otherwise, select All items to search through the entire active contact sheet.
Criteria: Optional - select additional criteria for searches that are case sensitive, restricted to whole words, or using Regular Expressions (Grep.) Regular Expressions are an advanced language for searches. Searching: Check to search Filenames, IPTC data, or both. (You must choose at least one)
When searching IPTC data, look through the following fields: Use this area to include or exclude specific IPTC fields.
When you are satisfied, the Find button will select those items for you in your open contact sheet. The Find window will remain open in case you want to refine your results or choose another contact sheet tab.