Lets go line by line
<!DOCTYPE html> - HTML5 Doctype
<html xmlns="http://www.w3.org/1999/xhtml"> - Refer here
<head> - Document head element
<meta name="Generator" content="some info here ..." />  Description of the program you used to create the HTML document
<meta charset="utf-8" /> - Document Character Encoding, Good read
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" /> Read Here And Here
I would've certainly wrote a big fat description for each but realized that these were already asked in different questions, so thought to link them instead of repeating the same thing here again.