Difference between library versions with same name-QNX 6.4.1

I installed 6.4.1 Momentics Development Suite (Windows host) and I searched for libc* in the C:\QNX641\target folder and it seems there are at least four different versions of libc like:

libc.so libc.so.1 libc.so.2 libc.so.3

What is the difference between the above?

There are other libraries also (like libcam.so*) which also have different versions.

They are older version of the library available on previous version of the OS 6.3.2, 6.3.0, etc (numbers have no relation ships). They are provided for backward compatibility so a 6.2 application can run on 6.4.1.