In simple terms an A/D converter samples an input analog signal and converts the value into a digital word at a sample rated determined by the particular A/D used and its clock rate. The sample rate has to be greater than 2 times the maximum analog signal frequency to avoid aliasing (generation of false sample words).
The device your are using is a specialized device designed for high speed, multiple channel applications such as medical/ultrasound imaging and doppler radar. It's a complex device and far from trivial to use. It includes an amplifier and anti-alias filter for each channel.
It will take much careful and time-consuming analysis of the data sheet to determine how to use the chip. If you have specific questions about its operation, perhaps someone can help you there. Just to say you don't understand a timing diagram, a memory map register, or a "Default Value" column is a little too general a question.