Yes, it is true. The object module is then linked into the final program along with the various routines required e.g. read/write. Suggest you get a beginners book - this will be explained. Something like COBOL for Dummies. I am not trying to be funny or rude - I use this book myself along with others. It comes with compilers for the PC so, if you do not have access to your normal machine then you can learn at home. One thing, it does seem to be a bit old now (1997) but the basics do not change!
Whilst researching this I came across SAMS Teach Yourself COBOL in 24 hours. Again an old book but again it has a PC compiler (which may not work with WIN/V WIN/7).
The problem I have is that people can explain things quickly but I can only comprehend slowly.