QA (Quality Assurance) is just software testing in IT field.

Software testing is a process to test software product manually or automatedly. The purpose is to test whether software products meet the specified requirements, and to find out any difference between expected results and actual results.
 
Software testing firstly needs to confirm quality of software. On the one hand, it validates whether this software product is the thing that users expect (Do right thing); on the other hand it is to verify that software product takes right way to do the thing (Do things right). Meantime, software testing can provide information, such as feedbacks for project managers to prepare for the risk assessment. It can be said that software testing is not only to test the software product itself, but also to test the software development process. If there is a lot of problem with a completed software product , it could mean that the development process is likely defective. Therefore, an effective software testing can ensure high quality of entire software development process.
 
Software engineers are both quality detectors and protectors during software development process. They are not only responsible to the final software product features and performance, but also need to analyze requirement, to check structural design and documentation at very beginning of software development, which reduce cost of software products, and assure high-quality software products to users.

Basic responsibilities of a QA tester should include following aspects:

 (1) Using various testing techniques and methods to test and discover defects that exist in a software product. Testing should be throughout whole software product development life cycle, including unit testing, integration testing, and system testing.
 (2) Reporting and assigning defects  to develope team for fixing when finding defects.  The most important thing of a defect report is to reproduce the defect for developers or other relevant people such as product managers, co-workers or customers. So testers must have good writing skills and language organizational capacity.

 (4) Analyzing the software quality after testing, according to test results including defect rates, defect distribution, and the trend of bug fixed; providing specified metrics including functionality, reliability, usability, security, time and resource characteristics; and finally giving a report to state whether the software product can be launched or released to customers.

(5) A person in charge of the project testing needs to develop a test plan, including test resources, test progress, test strategy, test methods, test tools, test risk and so on, in order to organize and implement testing effectively during testing process.
 
(6)designing test cases and preparing test data before testing beginning in order to ensure quality of the testing.
(7)Some automated testing would be used, and testers may need to learn how to use the automated testing tools, writing test scripts in order to improve testing speed and to reduce repetitive testing procedure.
 
(8) A test team leader may need to improve test facilities and train test team members to further improve test quality.