[ddreier]

I think your description is more accurate.

A Task is an individual unit of work: a container, executable, JVM app, etc.

A Task Group/Allocation is a group of Tasks that will be placed together on nodes as a unit.

A Job is a collection of Task Groups and is where you tell Nomad how to schedule the work. A "system" Job is scheduled across all Nodes somewhat like a DaemonSet. A "batch" Job can be submitted as a one-off execution, periodic (run on a schedule) or parameterized (run on demand with variables specified at runtime). A "service" Job is the "normal" scheduler where all Task Groups are treated like ReplicaSets.

Placement is determined by constraints that can be specified on each Task Group.