Difference between typedef enum and only enum

module top();

  // create a data-type called on_off_e which is derived from enum type

  typedef enum bit {OFF, ON} on_off_e;

  // create a variable of enum

  enum bit {CLOSE, OPEN} switch_e;

  // create a variable of data-type on_off_e

  on_off_e on_off;

  // If you try to define variable of switch_e then tool will give compilation error because switch_e it self is a variable

  //switch_e switch_val;

  initial
  begin
    $display("on_off=%s, on_off=%b", on_off.name, on_off);
    $display("switch_e=%s, switch_e=%b", switch_e.name, switch_e);
  end

endmodule : top

Output:

on_off=OFF, on_off=0
switch_e=CLOSE, switch_e=0