A flow consist of activities and sequences. The activities determine the generated logic, and the sequences determine the relationship between the activities. To add an activity to a flow, simply drag and drop an activity from the activity palette to the flow.
Sequences connect individual activities. Sequences allow you to set the order of a flow. An activity always needs one or more incoming sequences and can have one or more outgoing sequences.
Look for the green and blue highlights to see the usage of flow variables.
Green highlight means, the return variable or parameter from the selected activity is used here.
Blue highlight means, the return variable or parameter is used in the selected activity
Variable usage example