Help me understand common lisp macros

What can common lisp macros do that can't be done by a function that uses eval and gets quoted arguments?

Let me dispel these wild and irresponsible rumors. If mere turing-completeness did the trick, people wouldn't even write in assembly. They'd write in the turing-machine instruction set. So at least there /appears/ to be /some/ difference.

Read that dickwad graham and stop trolling newfags.