What is the distance_matrix of a coupling map?

What is the distance_matrix of a coupling map?
qiskit.org/documentation/stubs/qiskit.transpiler.CouplingMap.html

The coupling map is a graph which indicates the connectivity of the qubits in the hardware. The nodes in the coupling map represent qubits and the edges represent their connection.

For example:

The element $d[i][j]$ of the distance matrix for a coupling map represent the distance between $i$-th qubit and $j$-th qubit. The distance between 1 and 5 qubits is 2, so $d[1][5]=2$, you can follow the same logic to reconstruct the entire distance matrix.