What you're looking at is calculus, specifically differentiation. This is pretty core to understanding physics, because so much of physics depends on the time-e

What you're looking at is calculus, specifically differentiation. This is pretty core to understanding physics, because so much of physics depends on the time-evolving state of things. That's fundamentally what's happening here. The triangle, for example, is the upper-case greek letter delta, which in calculus represents 'change of'. You might have heard of 'delta-T' with respect to 'change of time'. In calculus, upper-case delta means 'change over a finite time' vs lower-case delta meaning 'instantaneous change'. The practical upshot, for example, is that the lower-case is the instantaneous rate-of-change at an instant in time, whereas the upper-case is the change over a whole time (e.g. the average rate of change per second for time = 0 seconds to time = 3 seconds). If you are trying to grok this, I would suggest an introductory calculus or pre-calculus resource. It doesn't have to be a uni textbook - higher-level high school maths usually teaches this. In this particular case, the Khan Academy would be my recommendation because it is about the right level (we're not talking esoteric higher-level university knowledge here) and it is eminently accessable. For example, this link may be a good starter in this instance: https://www.youtube.com/watch?v=MeU-KzdCBps https://www.youtube.com/watch?v=MeU-KzdCBps