If you want to have several articles on your site which are all introduced by a teaser-text (example:
http://www.gruene-os.de), than this is the more link which is opening the whole article.
To reach this feature you first have to go to the "Admin"-section to that special category and put the "article top...something" from -1 to something like 3 or 4. Than you should create 3 or 4 new articles in that categorie, all using this "more"-link.
cheers
By the way: PLEASE update to 1.2.6 (without DEV).