Window light
Simulator
Negative fill is black cloth where a bounce would go: it takes light out of the shadow side instead of adding it.
One source, no units
A window is a large, free, soft source that you cannot move. Everything about using it is choosing where the subject stands in relation to it, and what you put on the other side.
Distance decides evenness
Light falls off with the square of distance, so a face half a metre from a window is lit far more on the near side than the far. Step back and the two sides even out, because the ratio between the two distances shrinks.
Size decides softness
A window close to the subject is a large source relative to them, so shadows are soft and edges gradual. The same window across the room is effectively small, and the shadows harden.
The two pull in opposite directions
Close gives you soft light and rapid falloff. Far gives you even light and harder shadows. There is no setting that gives both, and choosing between them is most of the craft.
Bounce fills, cloth shapes
A white board on the shadow side returns light and opens the face up. Black cloth in the same place takes light away and deepens the modelling. Negative fill is the one most people never try.
Direction matters more than level
Turning the subject a few degrees toward or away from the glass changes the look far more than anything you can do with a bounce. Block for the light before you reach for anything.
It changes while you shoot
Cloud, time of day and the sun coming round are all working against continuity. If a scene matters, diffuse the window heavily so the source becomes the diffusion rather than the sky.