Shibuya station is one of the busiest stations in Japan, has the fourth highest number of passengers in Japan, most likely the fourth in the world too.
JR, Tokyu, Keio and Tokyo metro are operating at Shibuya station, total 8 lines are available at Shibuya station, including most busiest line JR Yamanote line and oldest subway in Asia, Tokyo metro Ginza line.
JR has three lines; Yamanoto, Saikyo and Shonan-Shinjuku lines but platforms of Saikyo and Shonan-Shinjuku lines are far from the Yamanote line's platform, therefore transfering at Shibuya station is not recommended. Also, it takes less time from Shinjuku to get to Shibuya by Saikyo or Shonan-Shinjuku lines than Yamanoto line but if you are going to the commercial area, it is faster to take Yamanoto line which is closer to the commercial area and also has more frequent number of trains running per hour.
Shibuya, one of the major commercial districts in Tokyo, is a place for young Japanese for shopping and dining, it has distinguished culture and life style compare to Ginza, which is high-end shopping and dining district in Tokyo.