Not quite the same, but close:
Think of Hardwood Briquettes as COMPRESSED lump charcoal.
LUMP CHARCOAL - Usually less dense than briquettes, because it has not been compressed. This is the "rawest" form of charcoal. If it is made from wood - the wood is simply carbonized (burned slowly in a low-oxygen environment) and the resulting charcoal is broken-up into chunks.
Lump charcoal is usually less dense and burns hotter and quicker than briquettes in most cases.
HARDWOOD BRIQUETTES: Like I said, it is essentially Lump Charcoal / Charcoal "dust" that has been compressed into briquettes. This process usually needs some sort of "binder" to hold the briqs together - some are more "natural" than others. Like Kevin said above - the better ones use a natural starch binder, which is really not so much a "chemical". This stuff should normally give you a bit longer burn time than lump in most cases.
Not all Briquettes are essentially, ALL hardwood charcoal - some contain coal dust and other fillers that are not supposed to be harmful for cooking. Burn a pile of Kinsford, then burn an equivalent pile of an all-hardwood charcoal, and then note the difference in left-over ash. The hardwood stuff will burn-down to practically nothing.