What does it mean to prefix a string with F?

Today's learning class , Find the following expression ：

msg = f"{self.name} serves wonderful {self.cuisine_type}."

print(f"\n{msg}")

# Precede string with f, Is to allow adding pytho expression , Of the above cases "self.name" It's not a string , It's a variable .

Let's take a simple example ：

Run the following program

Output is ：

str1 The output is zero 1+1=2

str2 The output is zero 2=2