Lemmy uses markdown formatting (for the most part, some things were added). Therefore:

A line break is two spaces at the end of your line

> This is a line.  
> This is another line.

This is a line.
This is another line.

A paragraph is two presses of the Enter key.

> This is a paragraph.
> 
> This is another paragraph.

This is a paragraph.

This is another paragraph.

To add a new line, you need to either add 2 spaces on the previous line or press enter twice.

Example 1. This is a first line, I add 2 spaces at the end
New line here

Example 2. After this line I press enter twice

New line here

Lemmy uses the CommonMark markdown spec. It is documented in the Lemmy documentation.

There is way to implement tables but I haven't found any official info. It is explained in this post - https://lemmy.ca/post/743625

Got it.
Thanks

It's not the simplest way to post something.
Will turn away lots of folks, i suppose. But it's doable.
I'm enjoying Lemmy a lot ;)