Intrinsic identity is pretty simple, conceptually. If a thing has it, its identity does not depend on something external to that thing. It can be aliased, referenced, renamed, what-have-you, but it still maintains whatever that "identity" is. People (most of them, anyway) have intrinsic identity. You are you, no matter what your name is, or where you live, or what physical transformations you may have suffered in life.
An electron, on the other hand, has no intrinsic identity. Perhaps introducing quantum mechanics here just confuses the issue, but I think it's a really fantastic example. There's no way to "tag" or "label" an electron such that we could tell the difference between it and a neighbor. If you replace one electron with another, there is absolutely no way to distinguish the old one from the new one.
Back to computers: an example of "intrinsic identity" might be the value returned by Object#hashCode()
in Java, or whatever mechanism a JavaScript engine uses that permits this statement to be false:
{} === {} // false
but this to be true:
function foo () {}
var bar = foo;
var baz = bar;
baz === foo; // true