What is the difference between defn and defmacro?

Question

What is the difference between defn and defmacro? What is the difference between a function and a macro?

Answer 1

defn define a function, and defmacro define a macro.
Macro is like a function but treat it's argument (if they are expressions as data), then process them and return data (list of symbols which are the code) and then evaluate that return code. So it's replace one code with another (on compile time).