There is a small difference between typing poetry into a website as opposed to typing prose.
The difference is line endings. With prose, a line ending indicates the end of a paragraph. On this site, as others, this causes a gap to be inserted between the paragraphs.
When entering poetry, this is not always what we want.
We would like the lines of a stanza to be next to each other.
As these four lines are.
So how do you make this happen?
The answer is very simple, and it is also true when typing into a word processor such as Word. To start the next line without causing a paragraph break, hold a 'Shift' key when pressing 'Enter'. This indicates a new line but not a new paragraph.
You might have thought that you have been using Word, for example, without doing this and it hasn't caused the gaps between paragraphs. That is simply because the formatting of the document has not been defined to produce a gap. Find the 'Format paragraph' setting and you will find a setting for gaps both before and after paragraphs. Change these and you will see the effect. If you have a document open when you do this and you want to affect that document, then select the whole document first.