Quality Assurance (QA): QA refers to the planned and systematic way of monitoring the quality of process which is followed to produce a quality product. QA tracks the outcomes and adjusts the process to meet the expectation.
Quality Control (QC): Concern with the quality of the product. QC finds the defects and suggests improvements. The process set by QA is implemented by QC. The QC is the responsibility of the tester.
Software Testing: is the process of ensuring that product which is developed by the developer meets the user requirement. The motive to perform testing is to find the bugs and make sure that they get fixed.