In macOS Monterey, with Full Keyboard Access enabled, you can use the tab key or other keys to maneuver through your Mac and each UI element effortlessly, rather than using your mouse or trackpad. Full Keyboard Access allows you to highlight an item on the screen that's focused, you can also customize the size, color, and contrast of the highlight itself.
Turn on Full Keyboard Access
Click the Apple menu
Click System Preferences > Accessibility > Keyboard > Navigation
Toggle the checkbox for Full Keyboard Access
To customize the appearance of Full Keyboard Access, click Options. To see the full list of shortcuts for Full Keyboard Access, click Commands. You can quickly view the list for shortcuts by pressing Tab-H, and using the arrow keys to navigate.