What does "document count" in the devtools refer to?

Question

You can see the word "Document Count" in Chrome DevTools.

_{(source: chrome.com)}

What is it?

For example, recording the below website, the number of documents is 8 or 9. https://developers.google.com/chrome-developer-tools/docs/javascript-memory-profiling?hl=it#dominators

This is a question of a tool but I think this could be a question of HTML, so I'm asking here.

Answer 1

The "Document Count" maintains a count of the number of documents used by your application over time, that are held in memory (not garbage collected). Iframes on your page along with their documents are also counted here. This counter may contribute in helping you identify what events in your application may be leading to a memory leak.

Please see the link below: https://developers.google.com/chrome-developer-tools/docs/timeline