I have some trouble in using org-mode. I want create a table in org-mode like this:
| operator | use         |
|----------+-------------|
|   |      | expr |         
        
To insert a vertical bar into a table field, use \vert or, inside a word abc\vert{}def.
Source: Org-mode manual: The built-in table editor.
If \vert is not automatically converted to |, call org-toggle-pretty-entities, per:
C-c C-x \
Toggle display of entities as UTF-8 characters. This does not change the buffer content which remains plain ASCII, but it overlays the UTF-8 character for display purposes only.
Source: Org-mode manual: Special symbols
The function org-toggle-pretty-entities was introduced in version 7.01. Call org-version and upgrade Org-mode if necessary.