itemize vs list

list is a basic LaTeX environment used to create list environments of all kinds, including itemize, enumerate and the description environments, as well as the 'trivial' list environments used for such things as quotations and abstracts.

You don't usually use the list environment directly in documents. Instead, it is used to create higher level environments, such as itemize, for use in documents.

Before packages such as enumitem were available, custom description, itemize and enumerate environments were created in this way. (Of course, they still can be, but enumitem makes it unnecessary in most cases.)

Here's an example specifying a simple variant on the description environment.

\documentclass{article}
\makeatletter
\newcommand{\labelpethau}[1]{\textsc{#1:}}
\newlength\normalparindent
\setlength\normalparindent{\parindent}
\newenvironment{pethau}%
{\begin{list}{}%
    {\renewcommand{\makelabel}{\labelpethau}%
      \setlength{\itemindent}{0pt}%
      \setlength{\leftmargin}{0pt}%
      \setlength{\labelwidth}{-1\normalparindent}%
      \addtolength{\topsep}{-0.5\parskip}%
      \listparindent \normalparindent
      \setlength{\parsep}{\parskip}}}%
  {\end{list}}
\makeatother
\begin{document}
\begin{pethau}
  \item[Question] some of what?
  \item[Answer] anything.
\end{pethau}
\end{document}

The itemize environment is a special case of the list environment. The list environment is more general: you can do more things with it. For instance,

\documentclass{article}

\usepackage{xcolor}

\begin{document}

\begin{list}{\color{blue}$\heartsuit$}{\color{red}}
\item first item
\item second item
\item third item
\end{list}

\end{document}