The San Diego Chargers are an National Football League team in the American Conference West together with the Oakland Raiders, Denver Broncos and Kansas City Chiefs. Overall, the Chargers are an average team. Either they have a really good season like 1994-95 (when they won the American Conference Championship and played in the 1995 Super Bowl) or they have a really lousy year.
The San Francisco 49ers are a National Football League team. They are in the National League West together with the St. Louis Rams, Arizona Cardinals and Seattle Seahawks. Because the 49ers finished atop their division at the end of the 2002 regular season, they earned the right to play in the postseason.
The Oakland Raiders are one of 32 National (American) Football League teams. They are in the American League West together with the Denver Broncos, Kansas City Chiefs and San Diego Chargers. The Raiders finished the 2002 regular season with the best (win-loss) record in their division, thus automatically qualifying them for the postseason.