What is the difference between Black Box Testing & White Box Testing?

First of all Black-Box and White-Box both are Test Design Methods.

“Black-Box” test design treats the system as a “Black-Box” (Wherein the tester can’t see as
to what is there inside the box). Hence we design the test cases in such a way that we pour
the input from one end of the box and expect a certain specific output from the other end of
the box. To run these test cases, the tester need not know as to how the input gets
transformed to output inside the box. Black-Box is also known as Behavioral-Box or
Functional-Box or Opaque-Box or Gray-Box or Closed-Box.

Whereas “White-Box” test design treats the system as a Transparent Box, which allows
anyone to see inside the “Box”. In White-Box the tester is able to see the process of
transformation of an “Input” into an “Output” inside the box. Hence we design the test
cases with a view to test the internal Logic, Paths or Branches of the box. White-Box is also
known as Structural-Box or Glass-Box or Clear-Box or Translucent-Box test design