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 ### Documentation & Guides
 * [API Configuration Guide](docs/api-guide.md): Detailed reference for configuring WorkerPools, ActorTemplates, Secrets, and Volumes.
 * [Full CLI Documentation](cmd/kubectl-ate/README.md): Installation and usage for `kubectl-ate`.
+* [Glossary](docs/glossary.md): Core terms (Actor, ActorTemplate, WorkerPool, Worker, ate-api-server, atenet, atelet, ateom) and how they relate.
 * [Observability Guide](docs/observability.md): Guide to actor logging, metrics, and distributed tracing.
 
 ## Tour
diff --git a/docs/glossary.md b/docs/glossary.md
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+# Agent Substrate Glossary
+
+This document defines the core terms used across Agent Substrate.
+
+For how the pieces fit together, see the [Architecture](architecture.md) and
+[API Guide](api-guide.md).
+
+## Resources (declarative, Kubernetes CRDs)
+
+- **ActorTemplate**: the definition of an actor "class": the container image(s)
+  and snapshot configuration. Creating an `ActorTemplate` triggers creation of
+  a [Golden Snapshot](#snapshots). It is treated as immutable: you create a new
+  template for a new version rather than editing an existing one. It is
+  analogous to a Pod template, but for a checkpointable workload.
+
+- **WorkerPool**: declares warm compute capacity, a fleet of pre-started worker
+  pods. It is reconciled into a Kubernetes `Deployment` by the
+  [atecontroller](#components).
+
+## Records (dynamic state, in the control-plane store)
+
+These are not Kubernetes objects; they live in the control-plane database
+because they change too frequently for etcd.
+
+- **Actor**: a single instance derived from an `ActorTemplate`, identified by a
+  DNS-1123 actor ID. It is the unit that is suspended and resumed, and it moves
+  between workers over its lifetime. An Actor record tracks its lifecycle
+  status and snapshot references.
+
+- **Worker**: a record representing one worker pod in a `WorkerPool`. A Worker
+  hosts at most one Actor at a time; many Actors are multiplexed across a pool
+  over time.
+
+## Components
+
+- **ate-api-server** (binary `ateapi`): the control plane. It owns the Actor
+  lifecycle, schedules Actors onto Workers, and coordinates their snapshots,
+  all backed by the state store. The `kubectl-ate` CLI talks to it.
+
+- **atecontroller**: the Kubernetes controller that reconciles the CRDs (for
+  example, it turns a `WorkerPool` into a `Deployment`).
+
+- **atelet**: the node-level supervisor, run as a DaemonSet. It pulls images,
+  assembles OCI bundles, drives the sandbox lifecycle on the node via ateom,
+  and streams snapshots to and from snapshot storage.
+
+- **ateom**: the coordinator that runs inside each worker pod and drives the
+  sandbox runtime on behalf of atelet. This decouples the physical pod
+  lifecycle from the sandboxed agent process.
+
+- **atenet**: the networking stack. It provides a DNS server for actor
+  resolution and a router that resumes suspended Actors on demand and routes
+  traffic to the right worker pod.
+
+- **podcertcontroller**: issues short-lived pod certificates that components
+  use as their TLS identity to authenticate connections to one another
+  (mutual TLS).
+
+- **kubectl-ate**: a `kubectl` plugin CLI for managing the Actor lifecycle and
+  listing Workers.
+
+## Lifecycle
+
+- **Suspend**: hibernate a running Actor by checkpointing it to a snapshot and
+  freeing its Worker.
+
+- **Resume**: activate a suspended Actor by restoring it onto a Worker. The
+  common path restores from a snapshot rather than cold-booting.
+
+## Snapshots
+
+- **Golden Snapshot**: the initial checkpoint captured once, when an
+  `ActorTemplate` is created, from a temporary "golden" boot of the workload.
+  By default an Actor of that template is first restored from this shared
+  snapshot.
+
+- **Last Snapshot**: the most recent per-Actor snapshot, written on Suspend and
+  used to restore that specific Actor on the next Resume.
+
+- **Snapshot storage**: the object store (GCS or S3) where snapshots are
+  persisted so Actor state is durable and portable across the cluster.
+
+## Networking
+
+- **Uniform DNS Mesh**: every Actor is reachable at a uniform address,
+  `<actor-id>.actors.resources.substrate.ate.dev`, resolved by atenet. Traffic to
+  that name is routed (and the Actor resumed if needed) automatically.