what does the built in map function do in Python code example

Example: map in python

# Python program to demonstrate working 
# of map. 
  
# Return double of n 
def addition(n): 
    return n + n 
  
# We double all numbers using map() 
numbers = (1, 2, 3, 4) 
result = map(addition, numbers) 
print(list(result))
# result [2, 4, 6, 8]