How to insert LaTeX symbols?

Question

Possible Duplicate:
How does one insert a backslash or a tilde into LaTeX?

I tried inserting symbols in latex. e.g.: \texttildelow

It didn't work. But symbols like \textasciitilde work.

I can't understand why some symbols work and others (the first one mentioned here) result in "undefined control sequence" error.

Answer 1

these symbols need the textcomp package:

\documentclass{article}
\usepackage{textcomp}%

\begin{document}
\texttildelow

\textasciitilde
\end{document}