The "int" instruction calls an interrupt. An interrupt is basically a signal to the CPU which stops it, and calls a special handler function (declared in the IDT, or Interrupt Descriptor Table).
On many UNIX-based OSes, interrupt 80h, or 128, triggers a system call (with the call number in EAX, and its arguments in EBX, ECX, EDX, ESI, EDI, and EBP). This is highly implementation specific, and could do anything in different OSes.
#bored