Additionally, there are many application notes and technical briefs available online that describe module functioning or introduce important features of a module. For example, the 5-Bit Digital-to-Analog Converter Technical Brief describes the DAC peripheral as relevant for the PIC16F and PIC18F microcontroller families.
Another example is the PIC16/PIC18 ADC2 Technical Brief. Other application notes and technical briefs can be found at Browse Application Notes - Microchip.