Manual Testing or simply Testing?
Speaking of manual testing is a fallacy since testing, quality assurance and control of any software product, must be carried out by the right people with the right knowledge. There is no other way to make a diagnosis of quality of a product if not with the intervention of experienced people. Of course this is not mentioning that at all stages of testing and quality control of a product it is possible to make use of tools including automation tools that will facilitate some of these tasks.
Having said that, we will refer generally to software testing as TESTING and the use of automation tools for certain tests such as automated testing.
The goal of testing is to ensure that the application being tested, is free of errors and is functioning according to the specified functional requirements.
Testing phases are also intended to ensure, that reported defects are fixed by developers, for further verification and validation.
Basically this system checks the quality and delivery of a product, as far as possible, customer error free.
Testing is an activity where specialists in charge have to be very patient, creative and open minded. They have to think and act with the perspective of an end user.