Obviously if you know Star Wars you know that means force, but I'll make it extra clear with the physics:
p is our momentum. It is known as the inertia of a moving object, and it is computed by p = mv (where m is mass and v is velocity).
By taking the differential with respect to time you're knocking the velocity part down to acceleration. We can check with the units: velocity should be m/s while acceleration is m/s^2. As to why I chose v and not m, it really doesn't matter. I just chose to knock v down because it'll be more important in the next step.
Everyone knows F = ma. But I know ma = F. We have mass. We have acceleration. We have them multiplied together. We get Force.
So the derivative of p with respect to time is F.