Locators are the 'addresses' used to find elements in the DOM. Selenium supports multiple locator strategies: ID (fastest, most reliable), Name (good for forms), CSS Selector (fast, modern), XPath (most flexible, can navigate backwards), Link Text (for links), Partial Link Text (for partial link matching), Tag Name (for finding all elements of a type), Class Name (less preferred). The hierarchy of preference for stability is: ID > Name > CSS Selector > XPath. Using a unique ID is the fastest and most reliable way to find an element.
Finding an element by ID is like looking for a house by its Social Security Number (unique and unchangeable). Finding it by XPath is like saying 'Go to the street with the park, turn left at the blue house, and find the third window on the second floor.' Much more complicated and fragile.
A developer changed the UI layout, and all your XPaths broke, but your ID-based locators still work. What does this tell you about locator strategy?