Focus lock, also known as focus trapping, is an important accessibility feature that ensures keyboard navigation remains within a specific component or part of the page. It is often used in scenarios where user interaction with other parts of the page should be temporarily disabled, such as:

Modals and dialogs: When a modal or a dialog is opened, users should be able to navigate only within the modal or dialog content using the keyboard. This prevents accidental interaction with the page behind the modal, which can lead to a confusing user experience, especially for screen reader users.

Dropdown menus: When a dropdown menu is opened, the focus should be trapped within the menu options. This ensures that users can easily navigate the menu items without inadvertently navigating away from the menu.

Off-canvas menus or sidebars: When an off-canvas menu or sidebar is opened, the focus should be locked within the menu or sidebar content. This prevents users from accidentally navigating to other parts of the page that are not currently visible or interactable.

Onboarding or guided tours: During an onboarding process or guided tour, the focus should be locked to the elements related to the current step. This prevents users from interacting with other parts of the page that may not be relevant at that moment.

Image or media galleries: When an image or media gallery is opened in a lightbox or fullscreen view, the focus should be locked within the gallery controls and content. This allows users to navigate the gallery without unintentionally interacting with the underlying page.

Wizards or multi-step forms: When a user is going through a multi-step process, such as filling out a form or completing a wizard, focus lock can be used to keep the user's focus within the current step, preventing them from interacting with other steps or parts of the page until they have completed the current step.

By implementing focus lock in these scenarios, you improve the usability and accessibility of your application, making it easier for all users, including those using assistive technologies like screen readers, to interact with your interface.