%% A mechanism in (La)TeX which you can also use to "separate out" other parts 
%% of your document.
%% Simply paste any number of lines into a new text file (say, file.tex) 
%% and then input it by putting:

\input{file}

%% in the place where the lines used to be (note you can leave out the .tex extension).
%% \input will act exactly like 'pasting' the file contents at the place it appears on.