basic atom pro

hi, i want to know some information about basicatom pro 28-M, in the overview features they mentioned that there hardware serial port 265 byte buffer and the 16 servo background control so i want know there function…and the meaning of the 0.5us timing resolution, and the meaning of the abbriviation us.
also the informations of the hardware I2C data input pin (SDA) and the hardware I2C clock pin (SDL) and the capture compare pin and the synchronous serial pin (sck)