BPMN tasks and activities

Activities are the rounded rectangles. The icon in the corner says who or what performs the work, which matters enormously once the process is automated.

An unmarked task is an abstract task, which is fine early and vague later.

#When it matters

Distinguishing work a person does from work a system does.
Any process heading for automation, where the marker decides the implementation.

#The symbols

Symbol	Means
Task	Rounded rectangle. A unit of work.
User task	Person icon. A human does it, usually in a form.
Service task	Gear icon. A system does it automatically.
Script task	Script icon. Runs a script in the engine.
Send and receive task	Envelope icons. Sends or waits for a message.
Manual task	Hand icon. Done by a person outside any system.
Business rule task	Table icon. Calls a decision, often a DMN table.

#A few things that catch people out

A loop or multi-instance marker at the bottom of a task changes its meaning; do not use it decoratively.
Business rule tasks are how BPMN and DMN connect. That is the clean way to model decisions.
If everything in your diagram is an abstract task, the model is still a sketch.

BPMN gateways

Diamonds: the path splits or joins.

BPMN sub processes

Collapsing detail without losing it.

BPMN notation reference

Back to the full symbol reference.

Sequence flow stays inside the pool.