If you create a page with a lot of text, maybe the page will get very long. You can shorten such a long page by only displaying some key points right away. ... Maybe the full text is of interest only to some people, for example to those who are especially keen on the topic in question. By hiding some of the text you will not bore the ones who are just flying lightly over it. For those who do open the full text, it will also prove useful to be able to collapse it and go back to where they left off.
Read More - or Less
Use plain text, not paragraphs, and a text-link for the dots. That is because you need to give them IDs - which is not so easy inside a paragraph.
The container .more-less-holder has no width limitation, but you may well give it a max-width.