The term 'mob' in anime and manga contexts often refers to background characters who exist to populate scenes without individual identities. These figures are usually drawn with minimal detail, sometimes just silhouettes or repetitive designs, creating a sense of crowded environments without distracting from main plotlines.
Interestingly, 'mob characters' serve as atmospheric tools—think of the faceless students in 'My Hero Academia' filling UA High's halls. Their presence reinforces the protagonist's uniqueness while maintaining world immersion. Some series like 'The Disastrous Life of Saiki K.' even parody this trope by having the protagonist perceive mob characters as literally grayed-out figures.