After start of <html> document there comes head section which starts with <head> and ends with </head> this is the area which will be not visible to you or your visitors in browser but this area contain very important things for your web page. Like the web title comes inside head section the title is what you see on top of your tab, head section contain your favicon , Not only favicon, title, but your head contain content description, meta tags for your search engine and other keywords , scripts, script files, styles, stylesheet , they do not appear on browser but they work in head section for your website to look it and work it as you want.