verification: To check whether we are developing a right 
product according  to customer requriements or not.it is a 
static process.
 
validation : It is the process of evaluating a software at 
the end of the SD process to ensure its compliance with the 
software requirements.it is a dynamic process.In simple 
words it is nothing but To check whether we have developed 
a right product according  to customer requriements or not.

quality assurance: It is nothing but the necessary actions 
we take to provide a product that is of the type and 
quality needed and expected by the customer.

Quality control: The operations and actions we take to meet 
the quality requirements.

test strategy: It is a planning done to approach the 
testing process.
test plan : It is a doc. which consist of 
scope,approach,resources,features to be tested ,features 
not to be tested, test environment, approval etc... In 
simple words  It is a doc. which consist of some rules and 
regulations to be followed while testing an application.