In China, passenger trains are numbered with special character and / or numbers, for example, Z305, K119, T8, 1008 and more, with these train numbers, the trains are designated into different classes.
Z train - overnight express, few or no midway stops. Z train is the most modern trains in China runs on some most popular routes such as Beijing - Xian, Shanghai - Xian, Beijing-Harbin. Such as Z15 from Beijing to Harbin.
T train - extra fast express, runs on most railways in China, only stops at major stations. It's a few slower then Z train for it has more stops. The train number looks like T + number , the number less then 400, then this train runs in multi railway bureaus, else if the number is from 401 to 999, then it runs in one bureau.
K train - fast express, has more stops then T train.
N train - intra-bureau fast express, has no difference with K train, except it runs in one railway bureau.
Number train - express and ordinary train.
1001 - 1999 - express, runs in 3 or more railway bureaus
2001 - 2999 - express, runs in 2 railway bureaus
4001 - 5999 - express, runs in 1 railway bureau
6001 - 8999 - ordinary train
L train - temporary express, runs in peak seasons such as spring festival holidays, national day holidays
A train - temporary train, runs according to the actual need and situation. You may not find an A train in schedule, however when buying a ticket, you may be told of this.
Y train - temporary tourist train, runs on special travel routes.
D train - MU (Multiple Units) high-speed bullet train, it runs during the day and has a top speed of 250km/h. Mostly they cover short distances ( around 200 km) however there are some long lines available, such as Beijing-Shanghai (1454 km) and Beijing-Harbin (1249 km).
Z train second class seat carriages
G train - the fastest high speed EMU bullet train, it runs on new-built high speed railways at top speed 350km/h. It only needs 3 hours 16 minites from Guangzhou to Wuhan (1049 km)
G train CRH engines and carriages
C train - Intercity high speed train, operates between two big cites such as Beijing - Tianjin, runs as fast as G train.
C train CRH engines and first class seat carriage