Welcome to indian railways thread- the arteries and veins of India..
I'm happy that you have a newfound interest for trains.
Ever since, i loved travelling by train, browsing through railway timetables was my hobby.
However, i was ignorant of the various locomotives and its features and started learning about them from wiki and irfca..
Just to start with, the locomotive model numbers come in an 'XYZ N' format..
The first letter denotes the type of gauge.
W- Broad Gauge
Y- Metre Gauge
The second letter denotes the type of locomotive-electric/diesel.
A- A.C Powered(electric)
and the 3rd letter denotes the purpose the locomotive is used for.
G- goods trains
M- mixed-both passenger and goods
The number N denotes the variant or the version number..
There are more variants of the above.
Now for example, WAP 4 locomotive is an AC powered electric broad gauge locomotive used to haul passenger trains.
You can go through the links provided by our dear co forumers for more info..