Ceramic disc cartridges are simply two ceramic discs with holes through them. One disc is held in place while the other moves with the faucet handle. When the two discs are aligned, water can flow through the faucet. When they no longer line up, the water stops.
If your faucet or shower head leaks and you can't seem to fix it, it may be caused by a faulty toner cartridge. Most faucets and showers have separate control handles for hot and cold water and have ink cartridges. To remove them, turn off the water supply to the faucet. Then you can unscrew the faucet or the shower head. The cartridge is easy to spot and then pulled out with pliers. However, you will need the same replacement to suit your type of faucet. As long as you have the right ink cartridges, replacing them with older ones is an easy way to improve the flow of water from your faucet.