What the 0.100-inch pitch and 3 positions mean for your board
The 829265-3: As a receptacle with bottom or top entry, it accepts a mating pin header from either side of the board, which simplifies routing in tight enclosures where the header approach direction isn't fixed.
Gold mating finish and what it buys the design
The post finish is tin, standard for solder-joint reliability. The housing is polybutylene terephthalate (PBTP), a common insulator for through-hole connectors that holds up to wave-solder temperatures.