What is happening between receiving HTML and DOM ready?

What is happening between receiving HTML and DOM ready?

I've spend evenings on tuning my backend code to be served faster, yet
there's a gap in page loading time that am not familiar with.
Attached an image - please tell me what is happening in highlighted time
(between recieving HTML and DOM ready).
What I think it is - maybe it's DOM intself generating? But why so long?
Theres like 10 HTML tags in this testing page.

That's my markup:
<!DOCTYPE html>
<html lang="pl">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>#</title>
<meta name="keywords" content="a, b">
<meta name="description" content="cde">
<meta name="geo.region" content="PL">
<meta name="geo.placename" content="Warszawa">
meta name="geo.position" content="52;21">
<meta name="ICBM" content="52, 21">
<link rel="stylesheet" href="/Css/_global/Style.css">
<!--link rel="shortcut icon" href="/Gfx/_global/favicon.ico"
type="image/x-icon">
<link rel="shortcut icon" href="/Gfx/_global/favicon.gif"
type="image/x-icon"-->
</head>
<body>
<ul id="bredcrumbs"><li>domain.com</li><li>Home Page</li></ul>
Content
</body>
</html>