\documentclass[varwidth=true, border=2pt]{standalone}
\usepackage[utf8]{inputenc} % this is needed for umlauts
\usepackage[ngerman]{babel} % this is needed for umlauts
\usepackage[T1]{fontenc}    % this is needed for correct output of umlauts in pdf
\usepackage[margin=2.5cm]{geometry} %layout

\usepackage{pgfplots}

\begin{document}
\begin{tikzpicture}
    \begin{axis}[
            width=15cm, height=8cm,     % size of the image
            xlabel=mean,
            ylabel=variance,
            visualization depends on={value \thisrow{label} \as \label},
            % every node near coord/.append style={font={\tiny}},
            nodes near coords={\label},
            % nodes near coords align={horizontal}
         ]
          \addplot[scatter,
                   mark=*,only marks,
                   % nodes near coords*=\label,
                   % ... which requires to define a visualization dependency:
                   % visualization depends on={\thisrow{label} \as \label}
                   ]
                   table [x=mean, y=variance, col sep=comma] {data.csv};
    \end{axis}
\end{tikzpicture}
\end{document}