When we render a model in blender we can have at the most basic two types of lighting – Hard lighting and soft lighting which determines how harsh or soft the shadows are.

In hard lighting the bright areas appear very bright and dark areas (shadows appear harsher) appear very dark compared to soft lighting (shadows appear softer). Lets use point light source for example. If we use increase the radius of the light then it would be soft lighting and if we would decrease the radius of the light source it would be hard lighting.

In hard lighting – shadows are harsh
In soft lighting – shadows are soft

Here we can see when the radius of the light source is 0 the shadow seems to be very harsh on the object.

However when the radius is increased to 0.39 we can see the shadows become much softer.

Source (my blog website): https://insanelogs.xyz/posts/blender-hard-light-vs-soft-light-in-2min/