Every workspace has a default flow target and a current flow target. Initially, these are both the same. The default flow target of a workspace, typically a stream, is initialized and set current when the workspace is created. The current flow target is the source of all incoming change sets and the destination of all outgoing change sets.
In a typical workflow, change sets delivered by other team members to one of your workspace's flow targets appear as incoming change sets for your workspace, and change sets you create in your workspace appear as outgoing change sets destined for a workspace flow target. The set of incoming and outgoing changes for a specific workspace is a function of workspace flow targets and workspace contents, however, so if you change the flow target for a workspace, new incoming and outgoing change sets may appear, and existing ones may disappear. If your workspace includes change sets created by other users and those change sets are not present in a new flow target, they will be classified as outgoing even though you did not create them.
A workspace that never collaborates with another workspace or stream has no flow targets and cannot accept or deliver change sets. This sort of workspace, which is private to its owner, provides a way to manage changes and check them in (back them up) to the repository but not to share them.
By default, all components in a workspace use the current flow target. You can use the workspace editor to add flow targets or change their scope so that not all components use them. For example, you could specify additional flow targets for some of the components in a workspace, or decide that a specific component should not flow to or from specific flow targets. (Removing a component from all flow targets makes all changes to it private to the workspace).