\documentclass{article}
\begin{document}
Here is an equation environment:
\begin{equation}
E = mc^2
\end{equation}

A theorem environment:
\begin{theorem}
All primes greater than 2 are odd.
\end{theorem}

Centered text:
\begin{center}
This text is centered.
\end{center}

A quote environment:
\begin{quote}
To be or not to be, that is the question.
\end{quote}
\end{document}
