"About Me" would be a post that wouldn't really make sense as a regular post. So you make it be a "Page type" and it gets treated differently. It will not show up in the list of posts, and there is a widget that will let you put a list of Pages in the sidebar or header or whatever.

For example :)

Thank you very much for your quick response.
I understand the functionality of it know.

PS.
Do you know if there's some option that allow a post to be saved as an html file and not (only) into DB?
My question goes because static pages are preferred from a SEO point of view (AFAIK)

Nope.

There is a way to make a snapshot of the main entry page, but not each individual post. If you do that then each time you post you'd need to do it again.