The HTML <main> element represents the main content of  the <body> of a document or application. The main content area consists of content that is directly related to, or expands upon the central topic of a document or the central functionality of an application. This content should be unique to the document, excluding any content that is repeated across a set of documents such as sidebars, navigation links, copyright information, site logos, and search forms (unless, of course, the document's main function is as a search form).

Note: 
<main> must not be a descendent of an <article>, <aside>, <footer>, <header>, or <nav> element.
Authors must not include more than one main element in a document.

Content categories:
Flow content, palpable content.

Permitted content:
Flow content.

Tag omission:
None; both the starting and ending tags are mandatory.

Permitted parent elements:
Any element that accepts flow content, but may not be a descendent of an <article>, <aside>, <footer>, <header>, or <nav> element.

DOM interface:
HTMLElement
