Meta Tags
Meta elements are HTML or XHTML elements used to provide structured metadata about a Web page. Such elements must be placed as tags in the head section of an HTML or XHTML document. Meta elements can be used to specify page description, keywords and any other metadata not provided through the other head elements and attributes. (Wikipedia)
Required
Character Set
Description
Responsive Support
Viewport
Historical
You are not penalized for these tags but they are not necessary in a modern web page