Black box Testing:

Testing done by the Software Testing (Team) Engineer on the 
functionality of the application/product with out the 
knowledge of the internal code is called 'Blackbox' 
testing. This testing includess both functional as well as 
non-functional testing. Non-functional is Security testing, 
performance testing, usability testing. 

Functional Testing:
This type of testing is called 'Functional' as the testing 
is performed on the functional aspects of the 
application/product with out the knowledge of the internal 
code. 

Back-end testing(Also called as 'Database Testing'):

This testing includes:
1. Checking the data entered through front end is  
successfully updated in the back-end.
2. Retreivin data from the back-end (Through some queries)
Note: To perfom back-end testing, the Testing engineer 
should have the knowledge of databases like SQL......

System Integration Testing:
Testing the system as a whole (Both functional & non-
functional)with the integration of all the modules/branches.

GUI Testing:
Testing the application/product with the end users 
perspective for :
1. Ease of use
2. User friendly
3. Look and feel

UAT: UAT is divided as Alpha & Beta testing
Alpha testing: 
Testing done by the Testing engineer at the developers site 
in the presence the customer.

Beta testing:
Testing done by the end user/customer at the customers 
site/environment without the presence of the testing 
engineer.

Performance testing:
Load & Stress testing are the sub sets of Performance 
testing.

Load testing:
Testing done with the specified load on the application to 
verify the application withstands the load at the given 
point of time.

Stress testing:
Testing done beyond the specified load on the application 
to verify the threshold point of the application.

Regards,
Imthiyaz. Shaik