Selenium Grid is a tool that allows for the distribution of test execution across multiple machines, enabling faster and more efficient testing. It was presented by Diego Molina, Staff Software Engineer at Sauce Labs, in an August 2021 webinar. The Selenium Grid can be either built or bought, with its own set of advantages and disadvantages. Building a Selenium Grid can provide customization options but requires maintenance, while buying one eliminates the need for maintenance but may come with additional costs. The tool is compatible with Appium and can support multiple browsers and versions. However, it has limitations, such as not yet being compatible with Appium and requiring significant infrastructure to host locally. Sauce Labs offers a cloud-based alternative called Sauce To Go, which provides a more secure environment for sensitive data storage.