Cannot implicitly convert type "String" to "System.Windows.Forms.Label"

Question

What does this mean?
Im using windows form, and heres my code so far, Please help!

double number1;
            double number2;
            double result;

            number1 = double.Parse(textBox1.Text);
            number2 = double.Parse(textBox2.Text);

            result = Math.Sqrt((number1 * number1) + (number2 * number2));

            label1 = result.ToString();