The serial ATA has multiple advantages over its predecessor, the three main being its throughput, cable management and hot plug.
The old ATA standard is commonly referred to as parallel ATA (P-ATA).

The first serial ATA models, which appeared in 2003, allow a theoretical throughput of 1.5 Gbit/s, but have been designed to go much faster. The serial ATA II doubles its 3 Gbit/s throughput and then the SATA III appeared in 2009 to 6 Gbit/s.
The theoretical throughput of 1.5 Gbps is 187.5 MB/s; in practice, the 150 MB/s is not exceeded, which is only 17 MB/s more than the fastest parallel ATA : the ATA/133.

The main advantages of SATA compared to PATA :

-PATA shares the same data sheet with another device, potentially reducing the bandwidth of each of 50%
-The SATA tablecloth is much easier to use, and to place, than that of PATA due to its reduced dimensions.
-Parallel buses now have difficulties to increase their throughput due to a problem of synchronizing data rows. The serial ATA uses the new LVDS for signaling.
-For multiple hard drives, in SATA, each disk has the maximum allowed by its standard and that of the controller. The SATA II standard allows the use of port multipliers.

SATA II standards (convenient peak throughput ~ 300 MB/s) and SATA III (convenient peak throughput ~ 600 MB/s) become useful for use between multiple SSDS, whose throughput starts to exceed 400-500 MB/s for high-end models early 2012.

The biggest change from the parallel ATA is in the physical aspect of the cables used. The data is transmitted by 2 pairs (one pair for transmission and one for reception), protected by 3 wires of mass. These seven conductors are grouped on a flat, unflexible tablecloth with 8 mm connectors at each end.
It can reach a length of up to 1 metre. Compared to the short (45 cm) 40 cable or 80 parallel ATA wires, the airflow, and therefore the cooling of the equipment, is improved thanks to this lower cable width. The concept of master/slave ratio between devices has been discontinued.

Serial ATA has only one device per cable (point-to-point connection). Connectors have detrompers, so it is not possible to put cable connectors upside down. Some cables have locking, some are not. The absence of locking can cause an unexpected disconnection in case of manipulation, which is in any way strongly discouraged. The same physical connectors are used for 3.5 and 2.5 inch hard drives as well as internal desktop PC CD/DVD drives and recorders.

Serial ATA uses 8B/10B encoding to perform transfers, allowing to work on better frequencies.

Serial ATA-born hard drives require a different power connector, which is part of the standard. The standard power connector resembles that of the data, but more broadly.
A 3.3V power supply is added compared to the PATA, so it takes 15 pins to ensure three power voltages if necessary : 3.3V 5V and 12V.

A SATA I, II or III can be plugged into a SATA I, II, or III motherboard. The resulting flow rate will be that of the slowest element.
Ex. : a SATA III hard drive on a SATA II motherboard will have a motherboard-limited throughput of 300 MB/s.

It is an adaptation of the SATA Protocol for laptops, but also for devices using small hard drives or SSD. The mini-SATA connector is smaller than the SATA but offers the same performance. The mini-SATA looks very much like a mini PCI-Express card, it supports for the latest (2013) SATA III standard at 6 Gbit/s.

It is an adaptation of the SATA Protocol for the connection of external devices. Its main features are :

-Transmit voltage higher than the SATA standard (500-600 mV instead of 400-600 mV)
-Receiving voltage lower than the SATA standard (240-600 mV instead of 325-600 mV)
-Identical Protocol, in order to be able to use the same equipment
-Maximum cable length greater than the SATA standard (2 m instead of 1 m)

Several manufacturers offer combo jacks where the eSATA port shares the USB2 plug for space reasons. Since USB 3.0, the USB port is seriously competing with the eSATA port because it offers comparable or even higher flow rates by being more ergonomic because it includes power supply lines.

The micro-SATA interface is available for 1.8 \hard drives, especially for ultraportable and Tablet PCs. The micro-SATA connector resembles the smaller standard SATA connector, the power connector is more compact (9-pin instead of 15) and has a PIN located between pins 7 and 8. Theoretical transfer rates are 230 MB/s read and 180 MB/s write.