Weak symbols

[sar]

Hi,
Can any body tell me

Why we create weak symbols? What is the purpose?
Creating of weak symbols can lead to a code with errors right, even though it doesn't show error?
I have line of code as below:

Process Attribs[] __attribute__((weak)) = {0};

here Process is a structure and this is C code.

Could you please tell me what is the meaning of it?

Thanks,
sar