The selenium grid is used to execute the test pass using a large number of machines to run the tests evenly. For example, if you have the opportunity to set up 100 tests, you have set the selenium phase to assist 4 different machines (VM or personal body machines) to run those tests and you will have the opportunity to run your tests on the same machine for the fourth (approximately) time after your test set is completed.
The selenium grid additionally allows tests to be performed against different operating conditions and against different programs at once. For example, each 'network' of virtual machines can be maintained by supporting an alternative program. Thus, Machine includes Internet Explorer , Internet Explorer , recent Chrome, the latest Firefox. During the test package run, the selenium phase receives each test-program combination and assigns each test to run against its desired program.
The Selenium Grid allows you to run your tests equally on different computers against different systems. That is, it runs multiple tests simultaneously against different machines running different programs and working configurations. In general, the selenium grid improvement test scatter executions. It focuses on running the test execution of your tests.
More to the point, there are two reasons you should use the selenium-phase.