What is Black Box Testing? Are Functional and Usability Testing its types?
I am writing about testing, and I am confused about the following: What exactly is Black-Box testing? Are functional testing and Usability testing two different types of testing, and are they both types of Black Box testing? I have to perform two different types of testing procedures. Is it ok if I do functional and Usability testing?

I am writing about testing, and I am confused about the following:
What exactly is Black-Box testing?
Are functional testing and Usability testing two different types of testing, and are they both types of Black Box testing?
I have to perform two different types of testing procedures. Is it ok if I do functional and Usability testing?