Visual testing is the process of ensuring that a web or mobile application appears as intended to the end-user. It's essential for developers to visually inspect their UI and detect any changes, both intentional and unintentional. This is crucial because automated functional tests may not catch visual problems, which can lead to issues like visual regressions. Cross-browser testing is also necessary due to the varying combinations of operating systems, viewport sizes, and browsers. Visual testing solutions automate this process by taking image snapshots and detecting any visual regression, making it easier for developers to identify changes and ensure a smooth user experience.