charset: Specifies the character encoding for the HTML document.
http-equiv: Provides an HTTP header for the information/value of the content attribute.
Edge mode tells Internet Explorer to display content in the highest mode available. With Internet Explorer 9, this is equivalent to IE9 mode. If a future release of Internet Explorer supported a higher compatibility mode, pages set to edge mode would appear in the highest mode supported by that version. Those same pages would still appear in IE9 mode when viewed with Internet Explorer 9.
name: Specifies a name for the metadata.
The viewport meta tag: the key to preparing a page for mobile devices optimization
width: The width of the virtual viewport of the device. Enter a number (pixels assumed), or the keyword “device-width” to set the viewport to the physical width of the device’s screen.
initial-scale: The initial zoom of the webpage, where a value of 1.0 means no zoom.
For more information, see HTML meta tag.
solved What are these meta tags? [closed]