Quality Assurance / Software Testing :
Quality Assurance / Software Testing is the process done to ensure the quality of a product or project & ready to be used by a end user.
In other words
As the name indicates Quality Assurance is assuring the quality of a product/project by implementing the practical testing on it.
What is Quality?
In general Quality is an english word and has a meaning.
Every human involve in this quality during his/her daily life.
Example: If a person is willing to buy a mobile phone or a laptop , his first step is to collect his requirements , if any phone device matches the same specifications he will verify them like bluetooth, Gtalk , apps, Camera , Speakers etc. It is nothing but testing the device to check if it is meeting the Quality or not.
When coming to Software Testing terms
Quality is nothing but meeting end user requirements with out any defects or issues.