Though thought to be largely as you describe it I believe the Oort Cloud is still theorectical.
For the sake of argument: Its about a light year out and is the source of long-period comets. I don't know about other star sysytems, but it could conceivably be influenced by the gravitational tug of the rest of the Milky Way and possibly a close - passing star. Its grip by the Sun must be very tenuous at that distance though so possibly a larger star -system could disperse it.
It's named after a Dutch astronomer who theorised that because comets were so volatile they would not have formed in their current orbits and therfore there had to be an outside source or nursery. If memory serves he wasn't the first to bring up the idea but he definately popularised it.
It is probably made up from debris left over from the formation of the solar system that was somehow ejected, possibly by the inner planets.
The debris itself would probably comprise water and methane ice, frozen CO, ethane and possibly some very light rocky rubble. Whether it formed in one go or over a period of eons, I have no idea.
That's about all I know, or think I know about the Oort Cloud!
Chime in anyone who has better info!
