A Finder is used to find a tag on an HTML/XML page, a range of cells in a spreadsheet document, or an element in a JSON structure. Finders are used in steps, where they identify what part of the page the step should work on. The list of Finders of the current step is located in the "Finders" tab in the Step View.
Finders look very different depending on the kind of page they work on, and the finders for each kind are described separately. See Tag Finders for details on the kind of finders used with HTML/XML pages, Range Finders for details on the kind of finders used with spreadsheet content, and JSON Finders for details on JSON Finders.