The conversation scope is a bit like the traditional session scope in that it holds state associated with a user of the system, and spans multiple requests to the server. However, unlike the session scope, the conversation scope:
is demarcated explicitly by the application, and
holds state associated with a particular web browser tab in a JSF application (browsers tend to share domain cookies, and hence the session cookie, between tabs, so this is not the case for the session scope).
A conversation represents a task—a unit of work from the point of view of the user. The conversation context holds state associated with what the user is currently working on. If the user is doing multiple things at the same time, there are multiple conversations.
The conversation context is active during any JSF request. Most conversations are destroyed at the end of the request. If a conversation should hold state across multiple requests, it must be explicitly promoted to a long-running conversation.
For more about it : https://docs.jboss.org/weld/reference/1.0.1-Final/en-US/html/scopescontexts.html