Meaning of dollar sign in gnu assembly labels

Question

What is the meaning of a dollar sign in front of a gnu assembly label?

For example, what is the difference between mov msg, %si and mov $msg, %si

Answer 1

You use $(dollar) sign when addressing a constant, e.g.: movl $1, %eax (put 1 to %eax register) or when handling an address of some variable, e.g.: movl $var, %eax (this means take an address of var label and put it into %eax register). If you don't use dollar sign that would mean "take the value from var label and put it to register".