Name368 has a pretty good example there. Basically, delta seconds is there to make things frame rate independent. In order to use delta seconds for something like a movement speed, you would first need to establish a movement rate like 10m/s. Let’s say your frame rate is 60fps(0.01666s), then you’d multiply your 10m/s by 0.01666s, the seconds cancel out and you’re left with 0.1666m moved in that time frame. You also use it for nodes like “finterp to constant” and with similar nodes like that, they tend to have an interp speed that’s pretty much the same as the movement rate stuff that I was talking about. I’m not 100% positive, but I think the non-constant “interp to” nodes have a ramp up/down effect on them so keep that in mind.
The main difference between delta seconds and world delta seconds is that world delta seconds accounts for time dilation. So using my movement example earlier, if you were in a bullet time mode, that slows speed to 1/10, the moving object would only travel 0.01666m per tick, instead of the 0.1666m that it normally would.