Question: why adc is 10 bit?
Answer: 10 bit ADC means the data (digital value of analog input.. ) from it is a 10 bit number. Thus this ADC data can take 1024 unique values. 6 or 8 channel ADC in a microcontroller usually means: 6 or 8 pin of microcontroller can be used to received that many analog signal which can in turn be digitized.