\documentclass{article}
\begin{document}

\section{Introduction}
\label{sec:intro}

In Section \ref{sec:method}, ...

\section{Method}
\label{sec:method}

\begin{equation}
\label{eq:euler}
e^{i\pi} + 1 = 0
\end{equation}

In Equation \ref{eq:euler}, ...

\end{document}

