An Action is a single operation performed in a Workflow. Actions are executed sequentially one after another by default, with parallel branch execution available as a configuration option. When an action finishes, it returns a success or failure status (true or false). This status determines which outgoing hops the workflow follows next. Actions can also pass variables, lists of files, and summary rows to subsequent actions. See the Actions catalog for all available workflow actions.

A Hop links Actions in a Workflow or Transforms in a Pipeline. In Workflows, Hops operate based on the exit status of previous Actions, Hops in Pipelines pass data between Transforms.

Pipelines are the data workers of Apache Hop. Operations in a pipeline read, transform, enrich, clean, validate, and write data. A pipeline starts with one or more pipeline sources and runs every transform in parallel. Data travels between transforms along hops through in-memory row buffers, ensuring high throughput and automatic back-pressure. See Pipelines for detailed execution mechanics, engines, and production scenarios.

A Transform is a single unit of data processing inside a Pipeline. Typical transform operations include reading from databases or files, filtering rows, calculating values, performing lookups, joining datasets, and loading to destinations. All transforms in a pipeline run simultaneously in parallel. Pipeline sources generate rows without needing an incoming hop, while intermediate transforms continuously process streaming rows and pass them along hops to downstream transforms through in-memory row buffers. See Transforms for where to find the page of each transform.

A Workflow is the orchestrator of your data architecture. Workflows execute a series of actions sequentially by default (with optional parallel branches). Workflows manage control flow rather than streaming individual rows: they check prerequisites, prepare environments, execute pipelines, manage files, handle errors, and send notifications. Hops in a workflow decide which path to follow based on whether an action succeeded or failed. See Workflows for in-depth orchestration concepts, decision backtracking, and scheduling scenarios.