When you plot the readings you have a description of what is recorded.. Unfortunately, you wont be able to predict the results for the same phenomena in different conditions for example a more complex geometry, a different material, or combination of materials, and that is why Differential equations comes in handy. Imagine that you can Analise what is happening in a small fraction of a system, that you can model a mathematic law for that infinitesimal part of the system... that model will be a differential equation... Now you just need to adjust that model to the rest of the system, either by integration or differential calculus, meaning you apply that same law to the rest of system..