Meta tags
the official data tag for each web page that is found between the open and closing head tags in the HTML code.
Title tags
an HTML tag which contains a sentence of text describing the contents of its associated webpage.
Meta descriptions
what appears on SERPs describing the content of each page being linked to.
TIP: meta descriptions generally run about 160 characters. Don’t only use those characters well, but stick to that limit so that when the description appears in Google its not to cut off with ellipses.
Content
this is what the engine bots need to associate your page with a set of keywords and/or phrases.