Differential equations have been around for a while. So let me write this as a, maybe an algebraic equation that you're familiar with. Algebraic, an algebraic equation might look something like, and I'll just write a simple quadratic, say x squared, x squared plus three x plus two is equal to zero. The solutions to this algebraic equation are going to be numbers or a set of numbers. We can solve this as going to be x plus two times x plus one is equal to zero. So x could be equal to negative two or x could be equal to negative one. The solutions here are numbers or a set of values or set of values that satisfy the equation.