Oak

Typically you use oak to age wines and spirits adding complex buttery vanilla flavours and tannins to add mouth feel.  

Wines would have traditionally been aged in oak barrels.

Spirits like whisky and brandy have to be aged with oak to get their amazing flavours.  

Different oak will add different flavours.  You can even toast the oak to add extra flavours and colour.  Whiskey and Brandy makers may even flame their oak barrels with blow torches to char the oak to add extra flavours and colour.

Oak chips are fine oak sawdust which adds a lot of flavour quickly.  You can use them straight out of the packet or you can toast them in a frying pan.

Oak Spirals can be use post fermentation for ageing.  This is great if you want to age with oak but dont have an oak barrel.  Simply place the spiral in your demijohn and leave to infuse it flavours.

Oak Cubes are usually make from old oak barrels that have been used for ageing, but when the barrels come to the end of their life and cant be remade, then the staves get cut up into cubes and you can add these to your fermented wine, spirit or even beer.  Oak cubes tend to come in a variety of pre uses, red wine, bourbon, brandy, port, etc etc.  These cubes not only add the oak flavours, but also those flavours and aromas of the liquor that was held in the barrel.