How do LISP macros differ from others?

I constantly hear LISPers boast of the macro capabilities of LISP. How are they different from, say, the macros one can make in C?

>>9
>orders of magnitude slower
see link in >>6

>>10
idiot. The duality of syntax between macros and functions is a major thing in Common Lisp, which has second-class compiler-hook macros. It's actually what informs tons of designs in CL, like ((foo)) not being valid/funcall, lots about the CLOS works, the package system, etc.

your whole point is stupid anyway. Compilers don't think more like people do than interpreters do. I'd claim the opposite, actually.