What is the American slang for a conversation between several people?
The american slang for a conversation between several people is to make a dialoge
A conversation is a talk between two or more people. You can also have a chat with Sb, (note that right form for chat is 'have a chat with Sb') which us a friendly informal conversation. A discussion about sth is when you talk about something seriously. An argument is a discussion in which people disagree, often angrily.
The difference between assertive and passive people is that assertive people initiate and an action whereas passive people tend to shy away from initiating an action. For example, an assertive person will be more likely to strike up a conversation with a stranger whereas a passive person would wait for the stranger to initiate the conversation. In the latter case, the "stranger" would be the assertive person.