Activities
An activity represents work that a company or organization performs using business processes.
An activity can be atomic (it is not broken down into a finer level of detail) or non-atomic. Atomic activities are represented in the Process Editor by tasks. For more information about how BPMN defines activities and tasks, see http://www.bpmn.org.
When creating the process, each time a different person, group, role, or system does something, an activity is added to the process.
Activities may be triggered by events such as the receipt of an email, phone call or workflow item, and may involve making a judgement on the presented facts and performing an action (such as entering data to a computer system, phoning someone in the same or a different organization, and so on).
A task in a process diagram represents an atomic activity (one that cannot be further broken down). A task of an unspecified type looks like this in the Process Editor:
If the activities can be broken down into finer steps, they should be represented as Sub-Processes. The Activity Type is set in the Properties view.