Figures and Images in LaTeX

\usepackage{graphicx}

% Image at half the line width:
\includegraphics[width=0.5\linewidth]{photo.jpg}

% Fixed width:
\includegraphics[width=8cm]{diagram.pdf}

% Fixed height (aspect ratio preserved):
\includegraphics[height=5cm]{chart.png}

% Scale relative to original size:
\includegraphics[scale=0.5]{logo.pdf}

\begin{figure}[htbp]
  \centering
  \includegraphics[width=0.8\linewidth]{results.png}
  \caption{Experimental results showing accuracy over epochs.}
  \label{fig:results}
\end{figure}

% Reference it:
As shown in Figure~\ref{fig:results}, ...

\begin{figure}[htbp]
  \centering
  \begin{minipage}{0.45\linewidth}
    \includegraphics[width=\linewidth]{before.png}
    \caption{Before}
  \end{minipage}
  \hfill
  \begin{minipage}{0.45\linewidth}
    \includegraphics[width=\linewidth]{after.png}
    \caption{After}
  \end{minipage}
\end{figure}

% Declare a folder so you don't repeat the path:
\graphicspath{{images/}{figures/}}

% Now just use the filename:
\includegraphics[width=\linewidth]{chart.pdf}