Indirect characterization reveals information about a character through their actions, thoughts, feelings, or dialogue, rather than through direct statements about them. In this case, the example of indirect characterization is:
"Ivan Dmitritch imagined his wife in the train with a multitude of parcels, baskets, and bags; she would be sighing over something, complaining that the train made her head ache, that she had spent so much money. . . . "
This sentence provides insight into Ivan Dmitritch's thoughts and assumptions about his wife, allowing readers to infer her personality traits (e.g., possibly being fretful or concerned about money) without directly stating them.