The materials that make up a ceramic blade are very hard. So hard that they are the second hardest material only to diamond. After the blade is sharpened, it will keep its razor sharp edge without wearing out or becoming dull. However metal blades require consistent sharpening.
Ceramic material is not very porous. This keeps the blade from transferring odors from one food to another.
Ceramic blades are very dense. A quick rinse in warm water will get your ceramic knife cleaner than a thorough scrubbing on a metal knife.
Ceramic material is very light weight making use of the knife even easier.
Ceramic knives will not rust as metal knives will.