Currently I am reading through the Arm based ATSAM4L series datasheet, and in the sections BSCIF and SCIF I have encountered at least 8 different oscillators/clocks (see image below). I understand that an oscillator is necessary for a clock signal for the MCU, but why are so many different sources necessary for this MCU family and MCU's in general?

EDIT: And what are the functions of these specific oscillators?