Answer - When it is a grape!
Children - well I suppose adults do too - may confuse blackcurrants and the dried currants using in baking. These are not currants at all but are dried grapes. TheBlack Corinth grapes used are a very small, sweet, seedless, black grape from Greece.
Currants and gooseberries belong to the same family of plants called Ribes. Several ornamental plants also belong to the same family.
They are fairly easy to grow and require a similar methods of cultivation. A relatively new introduction to the family is a jostaberry which is a cross between a blackcurrant and a gooseberry.
I have now completed the page on the website about currants and gooseberries click here