It's basically when ur system seems to stop in the middle of a task and everything grinds to a halt...if you hit Ctrl+Alt+Delete to open the Task Manager, you can check the 'Applications' tab to see what processes are running and which are not responding...in other words identify the culprit.
Click to highlight any process that says 'Not responding' and then click the End Task button. This should get things moving again.
Try closing everything and then just opening that one offending application by itself and see if it still hangs the pc.
If the problem only occurs when u try to open multiple apps, then u might need more memory. Alternatively, if the app alone fails to run, it could be a bug. There's loads of things it could be...software or hardware-related, so if any of the above fails to work, come back and tell us what the application is that seems to be causing the problem, what ur OS is, how much RAM u have and CPU speed....etc.
It was in Burma, a sodden morning of the rains. A sickly light, like yellow tinfoil, was slanting over the high walls into the jail yard. We were waiting outside the condemned cells, a row of sheds fronted with double bars, like small animal cages. Each cell measured about ten feet by ten and was quite bare within except for a plank bed and a pot of drinking water. In some of them brown silent men were squatting at the inner bars, with their blankets draped round them. These were the condemned men, due to be hanged within the next week or two.