The dark centre of shadow is still called umbra.
No light from the lamp reaches the umbra.
It is surrounded by a fuzzy partial shadow or penumbra.
The penumbra varies in brightness-from very dark near the umbra(where not much light can reach it) to very bright at the outer part where more light can reach.

Shadows

Shadows are formed when some rays of light continue to travel in straightr lines,while other rays stopped by an object.
The kind of shadow that is formed depeds on the size of the source of light.

Can you see a dark shadow with sharp edges?
This shadow is called umbra

Light

What the light is???
Light is electromagnetic radiation, particularly radiation of a wavelength that is visible to the human eye. In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not.

Speed of light
The speed of light in a vacuum is presently defined to be exactly 299,792,458 m/s (approximately 186,282 miles per second). This definition of the speed of light means that the metre is now defined in terms of the speed of light. Light always travels at a constant speed, even between particles of a substance through which it is shining. Photons excite the adjoining particles that in turn transfer the energy to the neighbor. This may appear to slow the beam down through its trajectory in realtime. The time lost between entry and exit accounts to the displacement of energy through the substance between each particle that is excited.

Visilbe light is a form of energy that we can detect with our eyes.

Objects that produce their own visible light are called luminous sources(for example,the sun,other stars,lamps,television,glow-worms).

Other objects are illuminated by this light and reflected it into our eyes(for example,this page and objects in this room,and the moon).