SATA - Serial ATA is a serial technology instead of being parallel like IDE (Also known PATA - Parallell ATA), SATA is liked more over IDE hard drives because of its speed increase and its small wires that allow air flow instead of big bulky ribbons that the IDE hard drives have.
Can you imagine how much better airflow and how much tidy it would look with SATA cables instead of IDE?
I don't want to go into detail between serial and parallel technology, so you'll have to google it.