Volume

A box. The simplest way to tell the scene that something is there.

Size and placement

Three dimensions and a position. Use volumes for the things that occupy space without needing to be modelled in detail: a fence, a conveyor, a control cabinet, a machine the robot must reach around.

Collisions

A volume is most useful with collision on: it becomes an obstacle the planner must route around. That is what turns "the robot might hit the cabinet" into "the software will not plan through the cabinet".

Using it as an obstacle

Model obstacles slightly generously. A volume 20 mm larger than the real cabinet costs nothing and buys margin; a volume 20 mm smaller is a collision the software promised would not happen.

For anything shaped where a box is too crude, import the geometry instead.