TTL means through the lens, Information is feed through the lens into the metering sensor, where it's program to work with the flash sensor for flash light output. Forget about the i, E or A infront of the TTL. its about the same expect for improvement which makes it more intelligent.
High speed sync means that your able to take photo with flash above the flash sync speed. this feature is only available in high end Dslr etc D200, D2x..