Selenium Grid is a client-server based testing tool within the Selenium suite that enables automated cross-browser testing across various machines, browsers, and operating systems, allowing for parallel and distributed test execution. It overcomes the limitations of local Selenium WebDriver by allowing tests to run on different platforms and browser versions without the need to install them on a local machine. The setup consists of a single Hub, which distributes test cases to multiple Nodes based on specified capabilities, supporting scalable and maintainable test environments. Using Selenium Grid, developers and testers can achieve significant reductions in execution time and perform multi-combination testing. The tutorial also explains how to configure a Selenium Grid setup using Java commands and how to integrate it with the pytest framework for automation code. Additionally, it highlights the advantages of using cloud-based platforms like LambdaTest, which offers a scalable infrastructure for executing tests across over 3000 browsers, simplifying the process and reducing the costs associated with maintaining an in-house setup.