#Key concepts

A short glossary of the words Chester uses everywhere, and how the things they name fit together.

#How the parts fit together

flowchart TD
  subgraph Organise
    Pj[Project] --> Ar[Process area] --> Gr[Process group] --> Pr[Process]
  end
  Pr --> El["Elements<br/>(the steps of the diagram)"]
  El -. "a person fills in" .-> Fo[Form]
  El -. "calls" .-> Ac[Action]
  Ac --> Ad[Adapter] --> Sy[System]
  Sy --> En["Environment<br/>(address + credential)"]
  Pr -- "deploy" --> De["Deployment<br/>(frozen snapshot)"]
  De -- "start" --> In["Instance<br/>(one run)"]
  In -- "hands out" --> Ta[Task]

A process lives in a fixed hierarchy. Its diagram is made of elements, and an element may use a form or call an action of a system. Deploying freezes all of it into a deployment. Every start of a deployment is an instance, and an instance hands out tasks to people.

#Organising

Term	What it means
Project	The top of the hierarchy, for example one team or one programme of work.
Process area	A top-level topic inside a project, such as Order management.
Process group	A set of related processes inside an area. A process is created inside a group.

See Organise your work.

#Modelling

Term	What it means
Process	A business process drawn as a BPMN diagram, plus its master data: owner, tags, documentation.
Executable	A switch on the process. Off, the process is documentation only and can never be started. On, it is validated while you model and can run once deployed.
Element	One shape in the diagram: an event, a task, a gateway, a sub-process. Not every BPMN element runs — see Elements.
Form	What a person sees when they start a process or work on a user task. What they enter becomes data the process can use. See Forms.
Expression	A small formula that computes a value or decides a branch while the process runs. See Expressions.
Validation	The check Chester runs while you model. An executable process only deploys when it passes.

#Connecting

Term	What it means
System	An external application your processes talk to, such as an ERP or a CRM. It holds no address and no password itself.
Adapter	How Chester reaches a system: HTTP, webhook, GraphQL, email or an LLM provider.
Action	One operation an adapter can perform, such as Fetch customer. A service task calls an action.
Environment	Where a system is reached — its base address and credential for development, test or production.
Credential	A stored secret, such as an API key. It is referenced by environments and never shown again once saved.

See Systems and adapters.

#Running

Term	What it means
Deployment	A frozen copy of a process and everything it uses. The engine runs this copy, not the process you keep editing. Development deployments switch themselves off after 30 runs or 24 hours. See Deploying a process.
Instance	One run of a deployed process, from its start event to its end.
Task	A step that waits for a person. It appears in My tasks in the Execution app.
Catalog	A list of processes an administrator makes available to certain people, so they can start them. See Collaboration.
Agent	An AI model with a job, tools and optional knowledge. An agent is a process too: it is modelled, deployed and run the same way. See Agents.
Knowledge vault	A set of Markdown notes an agent reads while it runs. See Knowledge vaults.

#The two apps

App	What you use it for
Designer	Everything that defines a process: organising, modelling, forms, systems, agents, deploying, monitoring, users.
Execution	Everything that takes part in a process: starting it, working on tasks, following your own runs, chatting with agents.

See Find your way around.