A ballplayer giving an autograph. Why would a professional photographer want to photograph it? Many people get athletes autographs, it's an everyday occurrence. But this happened in 1946, and the place was Louisville, Kentucky. Afro-Americans were not allowed to drink from the same water fountains as whites, or use the same bathrooms. They were not allowed in the same hotels, restaurants, schools or hospitals. In short, Afro-Americans were considered (and treated) as inferior to whites in all respects. So when an Afro-American player appeared in an all-white baseball league, many fans and players were furious. Threats and riots were a constant concern.
When Jackie Robinson left the Louisville ball park where this photograph was taken (Robinson was playing then with Montreal which was in the same league as Louisville), he was met by an Afro-American entourage. They included a driver (he couldn't stay in an all-white hotel with the rest of his teammates), friends, perhaps a bodyguard or two, and a photographer among others. When the photographer saw a young white man approach Robinson for an autograph, this was something to be noted. Here was a white person looking up to an Afro-American with respect. It was an implied admission that, at least in certain areas, this Afro-American was better than he. In view of the times, it was an unusual event. So he photographed it.
On the surface, the photograph is of a young man getting Jackie Robinson's autograph. But beyond that, it symbolized much much more.