documentclass{article}

usepackage{lipsum}

newenvironment{foo}{%
}
{%
}

newcommand{listfoo}{
% Some code to list the content of the `foo` environments.
}

begin{document}

lipsum[1]

begin{foo}
bf Foo text 1
end{foo}

lipsum[2]

begin{foo}
bf Foo text 2
end{foo}

lipsum[3]

begin{foo}
bf Foo text 3
end{foo}

listfoo

end{document}