They are called an audience or attendees.
an audience
audiance
It is a "collective Noun"
A Flock
people gathered at this place because this is the place that you can read lots of books and you can get knowledge by reading books on the library.
The adult students gathered in the classroom for their evening lecture.
A stab in the light.
congregation
A crowd.
-Lecturing -Lectured _________ Or simply: to lecture. Lecture is a verb its forms are: lecture / lectures / lectured / lecturing
A fireplace. The same thing you call it. At least, that is what I have gathered from watching British television shows.
Chinese Students gathered to call for political reform.