You can put any expression inside the curly braces:
a = 5
b = 3
print(f"{a} + {b} = {a + b}") # "5 + 3 = 8"
price = 19.99
tax = 0.08
print(f"Total: ${price * (1 + tax):.2f}") # "Total: $21.59"
The :.2f is a format specifier. It means "show decimal places for this float." Format specifiers let you control number precision, padding, alignment, and more.
F-strings evaluate at runtime. The expressions are calculated when the string is created, not when it's printed.