D3 of 30 Days' ISTQB: Test types

There are four test types:

1, Testing of function(functional testing)
The function of a system (or component) is 'what it does'. This is typically described in a requirements specification, a functional specification, or in user cases. There also may be some functions that are 'assumed' to be provided but not documented, which should be tested as well.
Functional testing considers the specified behavior and is often referred to as black-box testing. But this is not entirely true, since black-box testing also includes non-functional testing.
Testing functionality can be done from two perspectives: requirements-based and business-process-based. Requirements-based-testing uses a specification of the functional requirements for the system as the basis for designing tests. Business-process-based testing uses knowledge of the business processes. Business processes describe the scenarios involved in the day-to-day business use of the system.

2, Testing of software product characteristics(non-functional testing)
Non-functional testing, as functional testing, is performed at all test levels.
Non-functional testing includes, but is not limited to, performance testing, load testing, stress testing, usability testing, maintainability testing, reliability testing and portability. It is the testing of "how well the system works".

3, Testing of software structure/architecture(structural testing)
The third target of testing is the structure of the system or component. The techniques used for structural testing are structure-based techniques, also referred to as white-box techniques. Control flow models are often used to support structural testing.

4, Testing related to changes(confirmation and regression testing)
When a test fails, it is reported, and then most often is fixed. We need to execute the test again to confirm that the defect has been fixed. This is known as confirmation test(also known as re-testing.) When doing confirmation testing, it is important to ensure the test is executed in the exactly same way as it was the first time.
After confirmation testing, we also need to check that the system has not regressed because of the change. Regression tests are executed whenever the software changes,either as a results of fixes or new or changed funtionality.