> ## Documentation Index
> Fetch the complete documentation index at: https://docs.slipway.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# Glossary

> Look up a term used across the slipway docs.

**Always-on.** A service that holds its pods around the clock rather than starting on the
first request. A plan capability. See [Plans](/plans).

**Apps base domain.** The parent zone public services are served under by default, giving
each one `<service>.<apps-base>`. See [Custom domains](/networking/domains).

**Archived service.** A service removed from a project, whose metrics, deploy history and
logs stay readable. See [Archived services](/projects/archived-services).

**Build inputs.** The fields hashed into a build's image tag: `rootDir`, `dockerfilePath`,
`dockerTarget`, `buildArgs` and the service's `env`. Identical inputs on the same commit reuse the
cached image.

**Build machine.** The CPU and memory a project's builds run on. See
[Build machine](/deploys/build-machine).

**Source.** One `slipway.yaml` — a repository (or image) at a branch, and the services
that file declares. A project's services can come from more than one source.

**Cutover.** The moment a public URL starts serving a new build.

**Deployment.** One attempt to bring a commit live, with a status, an event log and a map of
public URLs. See [How deploys work](/deploys/how-deploys-work).

**Disk.** Persistent storage attached to exactly one service. See [Disks](/data/disks).

**Environment variable.** A value injected into a container at startup. In slipway, set as a
literal in the spec or as a [variable or secret](/slipway-yaml/secrets-and-variables).

**Instance.** Not slipway vocabulary. What other platforms call an instance is a
[service](/services/overview) here, and what they call an instance type is a
[CPU and memory allocation](/services/compute).

**Mount path.** The absolute path inside a container where a disk appears. Only data written
under it persists.

**Organization.** Your tenancy boundary, anchored to exactly one GitHub App installation or
GitLab group. See [How it works](/how-it-works#organization).

**Preview.** A temporary copy of a project, or of one service, brought up for a pull request.
See [PR previews](/previews/pr-previews).

**Private network.** The per-project network every one of a project's services shares. See
[Service to service](/networking/service-to-service).

**Probe.** A startup, readiness or liveness check declared in `healthcheck:`. One of `http`,
`tcp`, `exec` or `grpc`.

**Project.** The unit that runs: one or more services deploying together into one isolated
space, sharing config and a network. See [Projects](/projects/overview).

**Provisioned size.** The capacity reserved for a disk, which is what you are billed for, as
opposed to the bytes actually written.

**Public port.** A port marked `public: true`, which gives its service a hostname at the
edge. At most one per service.

**Replica.** One pod of a service. Every replica runs the same image with the same
configuration. See [Scaling](/services/scaling).

**Resolution.** Expanding every `${secret.*}`, `${var.*}` and `${service.*}` reference to a
value at deploy time. An unresolvable secret or variable reference warns in the deploy log
and leaves the key unset; a managed database's missing password secret, the compose
required form `${NAME:?}`, and unresolvable `${service.*}` references still fail the
deploy.

**Rollback.** Re-shipping a previous deployment's frozen images and spec, with no rebuild.
See [Rollback](/deploys/rollback).

**Seed default.** The snapshot a cloned project's disk is created from. Never pruned by
retention.

**Service.** One entry under `services:`, of type `web`, `worker`, `cron` or `static`. See
[Service types](/services/overview).

**Service reference.** A `${service.X.field}` expression, resolved at deploy time in `env`
and `buildArgs` only.

**Sibling.** Another service in the same project, reachable by bare name.

**Sleep.** Scaling a web service to zero on idle, waking it on the next request. See
[Sleep on idle](/deploys/sleep).

**Snapshot.** A point-in-time copy of a disk, restorable in place or usable to seed a clone.

**Spec.** The `slipway.yaml` describing a repository's services. See
[Overview](/slipway-yaml/overview).

**Stored spec.** A spec slipway holds for you, for a repository with no committed file.

**Supersession.** Marking a previous deployment replaced once a newer one is healthy.

**Tracked branch.** The branch a source deploys from.

**Wakeable.** A service that can be brought back from sleep, which requires it to receive
HTTP. Only a `web` service with a public port qualifies.


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