These questions are not good questions for a sites like the ones on Stack Exchange. The reason that these are not good questions is because they are simple questions looking for basic information that can be found by doing a simple search of The Internet.
What is X?
Answer: Search for "what is X?" on the internet
Answer: Search Wikipedia for X
For most things Wikipedia is close to the truth.
I don't think that this site is meant to be another repository of basic information, but rather a place to come for answers to questions like
How would I implement Guerilla Testing for my product X, given y restriction?
How do I test for a specific security vulnerability with X testing framework?