For questions regarding the {adjustwidth} environment from the {changepage} package.
The adjustwidth environment from the changepage package can be used to locally change the left and right margins of a document. The environment takes two mandatory arguments that can be either positive (increase respective margin) or negative (decrease respective margin).
\begin{adjustwidth}{<change to left margin>}{<change to right margin>}
The starred variant adjustwidth* is useful for twosided documents and alternates the values of the margins between odd and even pages.
\begin{adjustwidth*}{<change to inner margin>}{<change to outer margin>}
The adjustwidth environment can also be used inside of a floating environment such as figure or table.
\documentclass{article}
\usepackage{lipsum}
\usepackage{changepage}
\begin{document}
\lipsum[4]
\begin{adjustwidth}{1cm}{1cm}
\lipsum[4]
\end{adjustwidth}
\lipsum[4]
\begin{figure}[htbp]
\begin{adjustwidth}{-0.125\textwidth}{-0.125\textwidth}
\rule{1.25\textwidth}{1cm}
\end{adjustwidth}
\end{figure}
\lipsum[4]
\end{document}
