  We present old and new characterizations of core spaces, alias worldwide web
spaces, originally defined by the existence of supercompact neighborhood bases.
The patch spaces of core spaces, obtained by joining the original topology with
a second topology having the dual specialization order, are the so-called
sector spaces, which have good convexity and separation properties and
determine the original space. The category of core spaces is shown to be
concretely isomorphic to the category of fan spaces; these are certain
quasi-ordered spaces having neighborhood bases of so-called fans, obtained by
deleting a finite number of principal filters from a principal filter. This
approach has useful consequences for domain theory. In fact, endowed with the
Scott topology, the continuous domains are nothing but the sober core spaces,
and endowed with the Lawson topology, they are the corresponding fan spaces. We
generalize the characterization of continuous lattices as meet-continuous
lattices with T$_2$ Lawson topology and extend the Fundamental Theorem of
Compact Semilattices to non-complete structures. Finally, we investigate
cardinal invariants like density and weight of the involved objects.
