When you have text content on a page, you structure it into paragraphs with the <p> tag. Without it, the browser treats all your text as one continuous block - no matter how many blank lines you put in your code.
<!-- This won't create two paragraphs: -->
Salesforce has several clouds.
Sales Cloud focuses on leads and opportunities.
<!-- They show up as one line. Use p tags: -->
<p>Salesforce has several clouds.</p>
<p>Sales Cloud focuses on leads and opportunities.</p>Each <p> gets its own block with spacing above and below, so the text is easy to read.
You might wonder why not just use div for everything - it also creates blocks. The difference is that <p> tells the browser "this is a paragraph of text" while div just says "this is a generic container." The browser adds spacing between paragraphs automatically, and screen readers treat them differently.
Use <p> for actual text content. Use div for layout and grouping. In LWC, most of your text will be inside paragraph tags, while the component structure will use divs.