The sum of $1 + 1 = 2$.

Would you like more details or have any questions? Here are some related questions:

1. What is the sum of $2 + 2$?
2. How do you add larger numbers, like $15 + 27$?
3. What is the difference between addition and multiplication?
4. Can you explain how to add negative numbers?
5. How is addition used in real-life scenarios?

Tip: When adding two numbers, their order doesn't matter—this is called the commutative property of addition!