mode-line in emacs

[James D]

Can someone explain what those end-of-line (dos, unix, mac, undecided)
annotations in emacs mode-line mean? Let me put it more clearly: I know LF
is the separation of lines convention for unix, CR for mac and CRLF for dos
(CR=carriage return, LF=line feed) but still it is not obvious to me what
exactly they mean and how they affect my files. I am writing a little book
using LaTeX and some of my files are marked dos, others unix. Is the final
output influenced by these options? Are they really options? How can I
change them? Please educate me.
Thanks
James D