what is "%s" in python code example

Example 1: python string format

string_a = "Hello"
string_b = "Cena"

# Index based:
print("{0}, John {1}"
      .format(string_a, string_b))
# Object based:
print("{greeting}, John {last_name}"
      .format(greeting=string_a, last_name=string_b))

Example 2: String Formatting with the % Operator

>>> name = 'Bob'
>>> 'Hello, %s' % name
"Hello, Bob"