Passenger trains are numbered by numerals with the capital Chinese phonetic letters in front. Different letters imply different trains like following:

D - Multiply Unit Train. With the high technology, D-trains are the fastest in China.
Z - Through Train. Z-trains seldom stop in midway, except some important stops. However there is no passenger service in the midway stops.
T - High-speed Train. T-trains only stop in the capital city of each province or big cities.
K - Express Train. K-trains only stop in the executive center of provincial cities and some important places of counties.
N - Fast Train. N-trains stops in most stations of the provincial cities. Ninety percent of these trains are equipped with air conditioning.
L - Passenger Extra (Temporary Train). L-trains will be open to traffic only in peak times, such as the spring festival, golden week and so on.
Y - Tourist Train. Y-trains are for the convenience of tourist and their destinations are the popular sights.