OpenAPI has a concept of (user) sessions. 

When an authorization token is issued it will contain an internal session id, that identifies the unique session. The session is always associated with the user (that provided credentials for the authorization token).

It is possible to have multiple sessions for a given user (by issuing multiple authorization tokens on the same user).

If an authorization token is renewed, it will maintain the same session.

Sessions are important to understand in relation to session capabilities

Streaming Sessions

A streaming session is a session coupled with a context id. 

A context id is a user defined id, that will be used when establishing a streaming connection and when setting up subscriptions (or deleting them).

There will always be a one to one correlation between a streaming session and a physical streaming connection.

It is possible to have multiple streaming sessions (e.g. multiple streaming connections) associated with the same (user) session, by varying the context id.

It is not possible (and not allowed) to setup multiple streaming connections using the same streaming session.

There are rules for context ids and streaming sessions. 

See the streaming documentation for more details on this.