what does a += 1 mean in python code example

Example 1: what does += mean in Python

x = 0
while x < 5: 
  print(x)
  x += 1   #the x += 1 expression is a shortend version for x = x + 1

Example 2: what does += mean in python

x = 0
while x < 5:
  print(x)
  x += 1