Taps drip. It's inevitable, like death and taxes. They seal using a rubber ring screwed down over the end of a metal pipe. Sooner or later the rubber is going to go hard, split or just wear away and it will no longer seal. Then water seeps through, and the tap starts dripping. Left alone the problem gets worse as the water wears away the valve seat. Then you'll have to either re-grind the valve seat(Do you own a valve seat re-grinder? Who would?) or replace the tap. Tedious in either case. But, it need not happen. Many taps now use ceramic discs.
How They Work
Instead of blocking the pipe by squeezing a piece of rubber onto the end of it, there are two slotted ceramic discs held down over the water supply pipe. The bottom disc doesn't move, while the upper disc is rotated over it by the tap mechanism. When the slots align the the tap is on, and when the slots don't align, the tap is off.
Why Are They Better?
There are advantages to this approach. The main one is that the discs are very hard and withstand the erosion of water very well. Hence they last much longer before needing replacement. Also, because the water flow is between the two discs, it's the discs that wear not the tap body itself. Because of the arrangement of the discs, it only requires a quarter turn to go from fully off to fully on and the operation of the tap is very light. This has the advantage that they are easy to turn on with the back of the wrist if you have dirty hands or for people with restricted movement.
Where they are Used
The ease of operation and the long life mean that most good quality sink mixer taps have been made using ceramic discs for a while, but basin taps with ceramic discs are surprisingly less common. The more use a tap gets, the more attractive the use of ceramic disc technology becomes. This is doubly true in hard water areas, which can be murder on traditional taps.
There are a few disadvantages. The discs do eventually wear out, but manufacturers seem to have standardised, so it is reasonably easy to get replacements. Basin taps are sometimes handed and sometimes not, and it can be annoying to have to work out which way to turn the tap in order to get water. They are also more expensive and not suitable for very low water pressure. The only other disadvantage is that if you are used to the old style taps, which need a number of turns to turn fully on, you may inadvertently turn the tap on more than you intended, you can get a unexpected full-on jet of water. Embarrassing!