Selenium Grid allows you run your tests on different machines against different browsers in parallel. That is, running multiple tests at the same time against different machines running different browsers and operating systems. Essentially, Selenium-Grid support distributed test execution. It allows for running your tests in a distributed test execution environment.

Refer below articles to understand about selenium Grid –

Introduction to Selenium Grid – What is Selenium Grid?

Setup Selenium Grid to run test parallel across platforms

How to run test cases in parallel on different platforms virtually?