Including images requires the graphicx package. Use \includegraphics{filename} to embed a PNG, JPG, or PDF file.

\usepackage{graphicx}
\begin{document}
 
\includegraphics{diagram.png}
 
\includegraphics[width=8cm]{diagram.png}
 
\includegraphics[height=5cm, width=8cm]{diagram.png}
 
\end{document}

Width and height scale the image; if you specify only one, the other scales proportionally. Omit both to use the image's native size (which may be too large for a document).

The figure environment wraps \includegraphics to add captions, labels, and automatic positioning. Figures float to the top of pages or to a dedicated figure page, keeping text around them.

\begin{figure}[h]
\centering
\includegraphics[width=0.8\textwidth]{diagram.png}
\caption{Example diagram}
\label{fig:diagram}
\end{figure}

The [h] positioning option means “here” (keep near the code); [t] is top of page, [b] is bottom, [p] is a dedicated figure page. LaTeX may move figures slightly to optimize page breaks.

\centering centers the image. \caption{...} adds a numbered caption (Figure 1, Figure 2, etc.) that appears below the image. \label{fig:diagram} lets you reference it: write Figure~\ref{fig:diagram} in text (the ~ prevents a line break between “Figure” and its number).

Captions are cross-referenced automatically. Compile twice for references to resolve.

Multiple images side-by-side use \begin{minipage}...\end{minipage}:

\begin{figure}[h]
\begin{minipage}{0.45\textwidth}
  \centering
  \includegraphics[width=\textwidth]{left.png}
  \caption{Left image}
\end{minipage}
\hfill
\begin{minipage}{0.45\textwidth}
  \centering
  \includegraphics[width=\textwidth]{right.png}
  \caption{Right image}
\end{minipage}
\end{figure}

Each minipage takes 45% of text width; \hfill adds space between them. Both sub-figures share the outer caption; to label them separately use sub-figures package.

Rotation: Use \rotatebox{90}{...} or \includegraphics[angle=90]{image} to rotate 90 degrees.

Image formats: LaTeX prefers PDF for vectors (sharp at all scales) and PNG/JPG for rasters. EPS (Encapsulated PostScript) works with older tools. Modern pdflatex handles PNG/JPG natively.