The first is very easy. Cassis is simply the French word for 'blackcurrant'. Wine professionals use the term cassis when they want to sound sophisticated. Obviously it is unforgivably pompous and if anyone catches me using it, please kick me in the shins. I recently saw a tasting note for a Cabernet that promised both blackcurrent and cassis - amazing what they can do nowadays. Unlike cassis, 'structure' is a really useful term and hardly pompous at all. It refers to the nuts and bolts of a wine, its tannin, alcohol, acid and the intensity of flavour. If a wine has a 'good structure' it means that these attributes are all in balance. Most often, wines are termed as having 'good structure' when they have lots of the above with a view to good cellaring potential.