A crowd is structured with one leader and a number of individuals.
The leader speaks at individuals and the individuals have no communication with each other. The message is controlled by the leader. For example, a politician speaking to an enormous audience. Another example is a celeb such as Logan Paul hosting a podcast. The only way for the viewers to communicate is to direct message him after. Logan may not even see it and therefore not reply. This is strictly one-way communication as the leader is speaking AT the audience.
What is a group or community?
In a community people usually join over a shared purpose.
People interact with one another and individuals' thoughts and opinions matter. We discuss and make decisions together. In a community, every individual is important. Individuals mentor new participants and help to referee disputes.