Difference between busses
The interrelationship of the different busses is roughly as follows:

                                               / SATA
CPU =&gt; Northbridge =&gt; PCI Bus =&gt; Southbridge =&gt;  IDE
                                               \ USB


Where the Northbridge and Southbridge are names given to the two main controller chips inside a PC.

IDE and SATA both perform the same job but through different physical media - they are for attaching hard drives etc.

IDE is "Integrated Device Electronics" - also known as "ATA" or "ATAPI" (ATA Peripheral Interface).

SATA is "Serial ATA" - the same ATA protocol but serial instead of parallel.

USB is a serial communications bus which can communicate with any number of devices, not just hard drives and other storage devices.  It speaks a completely different protocol to the ATA family.

PCI (and the derivatives PCIe, etc) are much closer to the CPU and generally provides much more direct access to the CPU.

Edit:

You can see how everything is connected together in Windows through the Device Manager set to View Devices by Connection: