I have been working in the field of gravitational research for 10 years now (in a senior outreach position, not as a scientist - my maths is to weak for relativity) but my job is to communicate the hard science to the general public.
So maybe I can recount some info I have collected on black holes over time:
- it is correct that a black hole does not release anything it manages to attract into the event horizon (except maybe Hawking radiation - I suggest googling that) but a black hole is not a real hole in the sense that things drop into a weird dimension.
- to all intents and purposes a black hole is indeed just a cosmic body (similar to a neutron star) made up of very dense matter. It just concentrates the force of gravity for the collected matter into a small area.
- a black hole will grow as it "swallows" stuff that falls in, adding instant credibility to the idea that there is something there which it can be added to. It becomes heavier and larger as the event horizon is pushed outwards. A black hole also does not swallow another black hole - when two black holes collide, they form a larger single black hole.
- the event horizon is defined as the zone of a black hole beyond which a light particle will inevitably "fall into" the black hole.
- so the black hole does not release any light it has captured (that is actually why it is called a black hole) because light has mass and gravity acts on mass. Again, this phenomenon happens only because gravity around the black hole is so concentrated - all matter attracts light but the force is mostly not strong enough to be noticed.
- the real problem with black holes is that they also do not release information (think of information as observable causality here) so ordinary physics don't work in a black hole. A black hole has a singularity in the centre in a mathematical sense - all sensible numbers rocket off to infinity. So the state of physics in a black hole is not understood.
By the way, the phenomenon of light bending around large masses is well known in astronomy because it can be seen in far-off galaxies: scientists can actually see what is behind them because light is bent around them! Google for Einstein ring or gravitational lens.
A couple of good interviews on black holes can be found on this site:
www.scienceface.org.
Best to start with Kip Thorne and Cliff Will.
An interesting fact which you may have picked up: our own galaxy has a supermassive black hole in the center! 3rd interview on scienceface.org!
Now if you were to ask about gravity that would be a REAL toughie!
Sascha