Bulk autophagy also called non-selective macroautophagy. During bulk autophagy, autophagosomes fuse with lysosomes or vacuoles resulting in the degradation of the cargo.
While during selective autophagy, the cargo is distinguished (mitochondria, ER, ribosomes, peroxisomes and etc.) and recognized by specific cargo receptors, or selective autophagy receptors, to connect with the autophagosome for degradation.
Here are two videos for more an explanation:
1) The mechanism of autophagy: https://www.youtube.com/watch?v=Gc9gx33GvF0&t=2s
2) Self-Eating Cell Research Wins Nobel in Medicine: https://www.youtube.com/watch?v=Ws0mOmfC9EU