I am reading whitebox AES. "Mixing Bijection" is one of the important definition. For example, I copy one paragraph here:
The look-up tables that incorporate bytes of round keys can be considered miniature block ciphers. The application of concatenated input and output encodings help these components achieve confusion, as defined by Shannon. To help them achieve diffusion, linear transformations are also composed at their input and output (these compositions are done before the application of the concatenated input and output encodings). An invertible linear transformation is referred to as a mixing bijection.
I have read the definition of bijection online, which is easy to understand. What means mixing bijection? Explain in "simple" English, better with an example.