<form method="link" > or <a>? What's the difference?

I saw that we can write:

<form method="link" action="foo.html" >
<input type="submit" />
</form>

To make a "link button".

But I know we can write:

<a href="foo.html" ><input type="button" /></a>

Which will do the same.

What's the difference? What's their browser compatibility?