While i was surfing the net i’ve found this article By Matteo Ferrone about Linux signals, that i want to repost:
A signal is an event sent by the kernel to a running program.
The signals can arrive at any time and software can choose what to do when it arrives: it can decide to ignore it or may decide to execute a signal handler and continue with what he did.
There are 31 different signals, and you can see them with:
Of these there are 6 to be known by system administrators: