Anecdote:
a brief recounting of a relevant episode, frequently personal or biographical. Anecdotes are often inserted into fiction or nonfiction as a way of developing a point or injecting humor


Example:
"Six decades ago in this enchanting hideaway, less than a mile downstream from where the Mormon steps meets the gulch, twenty-year-old Everett Ruess carved his nom de plume into the canyon wall below a panel of Anasazi pictographs, and he did so again in the doorway of a small masonry structure built by the Anasazi for storing grain. "NEMO 1934," he scrawled, no doubt moved by the same impulse that compelled Chris McCandless to inscribe "Alexander Supertramp/May 1992" on the wall of the Sushana bus."
-Into The Wild, Jon Krakaurer



Explanation:
Krakauer uses different anecdotes in his telling of the true story of Christopher McCandless. His main purpose of doing this is to provide valuable perspective to the reader's understanding of Chris McCandless and why he thought wealth/happiness was not from money, but from the spirit. This anecdote describes a man who did the same thing, this helps the reader get more information and helps them relate the two stories. Another purpose of this is to give more evidence and examples of the themes of rebellious youth, and finding joy and happiness through nature.