Changing matrix style

Using array and rotatebox

MWE

\documentclass{article}
\usepackage{amsmath}
\usepackage{graphicx}
\begin{document}
\[\begin{array}{ccc}
 \text{Users} & &  \text{factors}\\
    \rotatebox[origin=c]{90}{\text{Movies}}
    \begin{pmatrix}
    x_{11}       & x_{12} & x_{13} & \dots & x_{1n} \\
    x_{21}       & x_{22} & x_{23} & \dots & x_{2n} \\
    \hdotsfor{5} \\
    x_{d1}       & x_{d2} & x_{d3} & \dots & x_{dn}
    \end{pmatrix}
    &=&
    \rotatebox[origin=c]{90}{\text{Movies}}
    \begin{pmatrix}
    x_{11} & x_{12} & x_{13} & \dots  & x_{1n} \\
    x_{21} & x_{22} & x_{23} & \dots  & x_{2n} \\
    \vdots & \vdots & \vdots & \ddots & \vdots \\
    x_{d1} & x_{d2} & x_{d3} & \dots  & x_{dn}
    \end{pmatrix}
\end{array}\]
\end{document}

Maybe you liked:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
    \[
    \underbrace{\!
    \begin{pmatrix}
    x_{11} & x_{12} & \dots  & x_{1n} \\
    x_{21} & x_{22} & \dots  & x_{2n} \\
    \vdots & \vdots & \ddots & \vdots \\
    x_{d1} & x_{d2} & \dots  & x_{dn}
    \end{pmatrix}\!
    }_{\mathbf{R}_{\text{Movies}\times \text{Users}}}
    \approx
    \underbrace{\!
    \begin{pmatrix}
    y_{11} & y_{12} & \dots  & y_{1n} \\
    y_{21} & y_{22} & \dots  & y_{2n} \\
    \vdots & \vdots & \ddots & \vdots \\
    y_{d1} & y_{d2} & \dots  & y_{dn}
    \end{pmatrix}\!
    }_{\mathbf{Q}_{\text{Movies}\times f\text{-factors}}}
    \cdot
    \underbrace{
    \begin{pmatrix}\!
    z_{11} & z_{12} & \dots  & z_{1n} \\
    z_{21} & z_{22} & \dots  & z_{2n} \\
    \vdots & \vdots & \ddots & \vdots \\
    z_{d1} & z_{d2} & \dots  & z_{dn}
    \end{pmatrix}\!
    }_{\mathbf{P}^T_{f\text{-factors}\times\text{Users}}}
    \]
\end{document}