Usually this is a formal group of people who have the same professional interest.

通常这是一群具有相同职业兴趣的正式人员。

The parade on Inauguration Day is something like that, but there are a lot of formal and official groups – military and so forth – that participate in the parade.

就职典礼日的阅兵是类似的，但是有很多正式和官方的团体——军队等等——参加了阅兵。