How to label lines and columns of a matrix?

Question

How can I obtain the following representation?

Answer 1

This is a job for nicematrix:

\documentclass{article}
\usepackage{amsmath}
\usepackage{nicematrix}
\begin{document}
[
\begin{pNiceMatrix}[first-col,first-row]
& C & D \
C & b-c & -c \
D & b & 0
\end{pNiceMatrix}
]
\end{document}