what do u mean by a blackhole?

Answer 1

OK, lets start from the beginning
Stars are interesting 'cause there are two antagonize forces working on it:
The Gravity Field which is trying to collapse the star and
The Fusion Reactions happening in the core trying to explode the star
Why antagonize, cause when one is trying to implode the star, the other is trying to explode it, and there is some kind of balance... until the combustible that keeps the fusion reactions runs out
Then, the gravity field starts to do its work, the mass of the star begins to infinitely compress and the temperature begins to rise on a incredible way. Finally there is so many energy that the "bulk of mass" explodes. But the highly compressed core survives and is a "small" core with a humongous amount of mass.
As the mass inside the given region of space increases, its gravity becomes stronger... which means, the black hole keeps compressing itself as time passes by (due to the massive gravity field) and the mass is still the same but is the same mass on a smaller region of space which makes the gravity field become stronger and this makes the core to compress itself as time passes by but the mass is the same on a smaller.... well you get the idea. and What we have is a Unbelievable Strong Gravity field.
How Stronger?
So strong that even the light rays (which obviously travels at the speed of light) are sucked in! imagine something traveling at 300,000 KM/s through space and suddenly is being pulled! Amazing isn't it? So, since Light is sucked into the black hole we cannot see it. There is a conceptualization on the wikipedia you can see it on the links below.

So "A black hole is what remains when a massive star dies."
(Taken from How Stuff Works)

Answer 2

I copied this intro. from the article link below: "A black hole is a concentration of mass whose gravitational field is so strong that nothing can escape. Black holes are predicted by general relativity. Under the description provided by general relativity, as an object moves closer to a black hole, the energy required for it to escape continues to increase until it becomes infinite at the event horizon, the surface beyond which escape is impossible. Inside the event horizon, the geometry of spacetime is distorted in a way that makes moving closer to the central singularity inevitable no matter how the infalling object moves."

Answer 3

black hole is a concentration of mass whose gravitational field is so strong that nothing can escape. Black holes are predicted by general relativity. Under the description provided by general relativity, as an object moves closer to a black hole, the energy required for it to escape continues to increase until it becomes infinite at the event horizon, the surface beyond which escape is impossible. Inside the event horizon, the geometry of spacetime is distorted in a way that makes moving closer to the central singularity inevitable no matter how the infalling object moves.

The existence of black holes in the universe is well supported by astronomical observation, particularly from studying X-ray emission from X-ray binaries and active galactic nuclei.

It has been hypothesised that black holes radiate energy due to quantum mechanical effects (known as Hawking radiation).

Answer 4

The gravity of a blackhole is so strong that not even light can escape.
That's why they call it a blackhole.

Answer 5

An anomaly with a gravity field so dense that light itself gets sucked into it. The absence of light create a large "black hole" in space.

Answer 6

invisible in space which has soooooo much gravity than nt even light can escape from being sucked in..

Answer 7

big star with so much mass the light can not escape