Conversation is pretty neutral, although it does sound a little formal. -I had a conversation with her about it. We've sorted it out now, there is no need to worry. "Talks" sounds quite formal to me. It's often used in the news when covering governmental or political matters -The two countries are currently talks about the possibility of a nuclear attack I think "chat" is used most. -Do you want to have a chat? -I had a chat with my teacher yesterday about it, we have decided that... -Sorry I'm late! I was just chatting to my parents on Skype. Just like Chinese, there are many many words for "to speak" or "to chat". Laurence

"Conversation" is relatively formal, and implies that at least two different people will be talking and listening to each other. "Talk" is a little less formal, but only implies that at least one person will talk. For example, you might have a famous person stand in front of an audience and give a speech. You could call that a "talk", but not a "conversation". "Chat" is informal and similar to "conversation". It suggests at least two people are talking and listening.