what is difference between <a> hyper link and <link>?

Answer 1

<link> for linking to another resources or outer resources like stylesheet files or scripting files or define the relation of your document with other docs.
<a> to making a hyperlinks in you document usig images or text or anything

Answer 2

link used in the head tag for linking relevant files with your html DOM
whereas a anchor tag is used to create a hyper link on text images etc,