Accretion disks are a central feature in the discussion of black holes and their behavior. As matter falls into the strong gravitational fields of black holes, it forms a swirling disk around the black hole, known as an accretion disk. These accretion disks are important for observing and studying black holes, as the matter in the disk can emit radiation that is detectable by telescopes.
The podcast episodes "The Updated Physics of Black Holes with Steve Balbus & Andrew Mummery" and "Ep. 5: Black Holes" both discuss accretion disks as a key aspect of black hole physics and observation. The former episode goes into more technical detail on the role of instabilities and turbulence in the accretion disk, while the latter provides a more general overview of the importance of accretion disks in studying black holes.