ELI5: Explain Like I'm 5

Boundary value problem

Imagine you have a puzzle with lots of different puzzle pieces. But instead of being able to just put the puzzle together however you want, there are rules you have to follow. You have to put the puzzle pieces together in a certain order, and the pieces have to fit together perfectly.

A boundary value problem is kind of like a puzzle with rules. Instead of putting puzzle pieces together, we're trying to solve an equation (a math problem with numbers and symbols). But just like with the puzzle, there are rules we have to follow.

The "boundary" part of the name refers to the edges or limits of the problem. Think of a sandbox - the boundary would be the edge of the sandbox. In a boundary value problem, we have to solve the equation within certain limits or boundaries.

For example, imagine we want to figure out how fast a toy car will roll down a ramp. We know the height of the ramp (the boundary), and we know how heavy the car is (another boundary). We also know some other things, like the angle of the ramp and how much friction there is.

To solve this problem, we have to put all the pieces together - kind of like fitting puzzle pieces together - to find the answer. We have to solve the equation with all of these different pieces of information, which is the boundary value problem.

So in summary, a boundary value problem is a math problem where we need to find the solution within certain limits or boundaries. We have to fit all the puzzle pieces or pieces of information together in order to solve the problem.