When a human is not used for testing a particular module, then it means that we are using a tool for testing and when we use any tool for testing a module (software) then it is known as automated testing. Testing tools facilitate a software tester in different conditions where testing becomes critical. According to the circumstances, we choose software testing tools. There are many tools which are used for software testing like silk performer and win runner.
Testing tools can be used for different testing activities to automate them. For example, we can use testing tools for Load/Stress tests. As if we perform load testing and stress testing manually then don't you think that it is impossible to simulate a large number of users? Similarly as we perform regression testing whenever we change the code of a module, so it becomes difficult to do it manually. Thus for making the procedure of sanity testing automate we use testing tools. Similarly we can use tools for sanity tests as it is difficult to perform sanity testing on every build manually. Advantage of testing tool is that they save precious time, and also remove the chance for a bug to remain unobserved while testing, but your test cases must also be very powerful because testing tools automate test cases and if your test cases are weak, then testing tools cannot provide better performance.
Testing tools can be used for different testing activities to automate them. For example, we can use testing tools for Load/Stress tests. As if we perform load testing and stress testing manually then don't you think that it is impossible to simulate a large number of users? Similarly as we perform regression testing whenever we change the code of a module, so it becomes difficult to do it manually. Thus for making the procedure of sanity testing automate we use testing tools. Similarly we can use tools for sanity tests as it is difficult to perform sanity testing on every build manually. Advantage of testing tool is that they save precious time, and also remove the chance for a bug to remain unobserved while testing, but your test cases must also be very powerful because testing tools automate test cases and if your test cases are weak, then testing tools cannot provide better performance.