I read that heredoc is for long strings of text specifically multi lines. So are we talking quantity of text or formatting?

One example I read is that someone used to use heredoc for writing out sql strings in php, so they could read the query easier.

But I write queries all the time on multiple lines without a problem, without any form of concatenating:

$sql = "SELECT

I just don't understand if heredoc is for, say, a paragraph of text, or multiple lines ( formatting wise ), that need to echo out on the page in multiple lines.