problem In using functools in a code

[akbarza]

hi
in code:

# from: https://python.coderz.ir/lessons/l13-decorator-generator-and-lambda-with-python-functions.html
import functools
import time

def timer(func):
    """Print the runtime of the decorated function"""
    #
    @functools.wraps(func)
    #
    def wrapper_timer(*args, **kwargs):
         start_time = time.perf_counter()
         value = func(*args, **kwargs)
         end_time = time.perf_counter()
         run_time = end_time - start_time
         print(f"Finished {func.__name__!r} in {run_time:.4f} secs")
         return value
    return wrapper_timer


@timer
def waste_some_time(num_times):
     """This function only wastes some times."""
     result = 0
     for _ in range(num_times):
         for i in range(10000):
             result += i**2

if __name__=="__main__" :
    print(f" result of running command 'waste_some_time(1)' is :")
    waste_some_time(1)
    print()
    print(f" result of running command 'waste_some_time(999)' is :")
    waste_some_time(999)
    print(f"result of command 'waste_some_time.__name__' is: \
{waste_some_time.__name__}")
    print(f"result of  command 'waste_some_time.__doc__' is: \
{waste_some_time.__doc__}")

when a module is imported, for using its function, only the function is called. for example, I write:

import math
math.exp(1)

but in line 8 of the above code, there is @ functools.wraps(func). why this @is used for? I read about wraps a little value, but I did not understand it. for what we use this?
thanks