Usefulness of Matched $z$ transform Method
the Matched Z method is the simplest method to convert an analog filter design with transfer function $H_\mathrm{a}(s)$ to a digital filter design $H(z)$.  It does it by mapping every pole and every zero from the $s$-plane to the $z$-plane using:

$$ z \leftarrow e^{sT} $$

where $T \triangleq \frac{1}{f_\mathrm{s}}$ is the sampling period and the reciprocal of the sample rate, $f_\mathrm{s}$.  Stable analog filters get mapped to stable digital filters.  That's all that it is.

The other two common methods are the Bilinear Transform, which approximates the above mapping:

$$ z \leftarrow \frac{1+\frac{sT}{2}}{1-\frac{sT}{2}} \approx \frac{e^{\frac{sT}{2}}}{e^{\frac{-sT}{2}}} = e^{sT} $$

and the Impulse Invariant method which is a time-domain way of looking at things:

$$ h[n] \leftarrow h_\mathrm{a}(nT) $$