Assembly means a group of persons gathered together for a common purpose.
In this picture, I want to show that, on the left, there is a assembly. And on the right, there is a alone people.
This picture shows the freedom of assembly. It means that people can have the freedom or rights to choose which assembly they want to be in.
This freedom is important. Because if people have the freedom to assemble into groups, they can know many other people which have the same purpose with him/her. Assembly is a good way to find people which have the same purpose with you, so that you can have enough power and influence to do something tha you want to do. Because more people will make bigger influence and can effect more people. Different kinds of assembly can have different role. If there is a assembly which want to protest with the government, they have enough power to do that. Because there are too many people, and government can't stop all of them.