Barrique
A barrique is a small oak barrel in which wine is aged after fermentation. The word is used in particular for the smaller barrels, and unlike large wooden casks or steel tanks, the small barrels give the wine far more contact with the wood relative to the volume of wine. That means the oak leaves a clearer mark on the aroma, flavour and structure alike. A barrique can be new or used several times, and each time it is reused it gives less to the wine.
This matters for what you taste. Ageing on oak can add notes of vanilla, smoke and spice, give the wine more body in the mouth and make the colour deeper. How much you notice depends on the origin of the wood, how heavily the barrel is toasted on the inside, how many times it has been used and how long the wine rests in it. The small barrel also lets a little oxygen seep in over time, which softens the wine and helps the flavour mature slowly.
You can often recognise barrique ageing by the spicy, toasty or vanilla-like note that settles on top of the fruit. A common misunderstanding is that an oaky flavour is always a sign of quality. It is more a question of balance, so that the wood supports the fruit instead of drowning it out.