Beam -

In construction, a beam is a structural element designed to withstand loads primarily applied laterally to its axis. Apache Beam Programming Guide

Encapsulates the entire data processing task from input to output. In construction, a beam is a structural element

The data processing operation (e.g., filtering or grouping) applied to a PCollection. In construction, a beam is a structural element

Primary sources, data, or artifacts that you analyze or use as evidence for your claims. In construction, a beam is a structural element