The faster the disk spins, the lower the 'seek time'. 7200 is better than 5400.
ultra direct memory access
UDMA defines a new protocol for the interface between the hard drive and the computer. It improves upon the ATAPI/EIDE standard by doubling data transfer rates to 33MB/sec, which translates into faster disk reads and writes. For users to take advantage of UDMA, both their system and hard drive must support the protocol. UDMA retains backwards compatibility for previously existing hardware.
integrated device (or drive) electronics
This hard-drive interface has all of its controller electronics integrated into the drive itself. The IDE specification handles hard disks up to 504MB in size. Because of its simple instruction set and the short route between controller and drive, it's a quick and easy type of drive to use (unlike SCSI drives and the older Enhanced Small Device Interface (ESDI) drives from the late 1980s). But because it's a limited specification, IDE is gradually being superseded by an enhanced version, EIDE.
enhanced integrated device (or drive) electronics
A second take on the PC platform's IDE drive interface that increases the previous maximum disk size from 504MB to more than 8GB, speeds up the data transfer rate to more than twice what IDE was capable of, and doubles the number of drives a PC can contain, bringing the number up to four. On the PC platform, EIDE gives SCSI-2 a run for its money, and while most people agree that SCSI-2 is technically superior, EIDE is cheaper to implement, which gained it widespread acceptance.
Small Computer System Interface
While the PC was settling for rankly inferior alternatives, the Mac adopted SCSI as its expansion standard. With SCSI, you can add up to seven new devices to your computer and depend on them to deal with single-interface issues by themselves. It's a robust standard, and it's rendered even more so with its latest implementation, SCSI-2. But it requires some system overhead, slows down your computer's start-up, and demands that during installation you handle device ID administration and a process called termination that closes the SCSI circuit. Pronounced "scuzzy" by those in the know.
And then there's Serial ATA or SATA