Add more content to platform concepts lifecycle summary

content/docs/for-platform-operators/concepts/lifecycle/_index.md

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 include_summaries=true
 +++
 
-The `lifecycle` orchestrates buildpack execution, then assembles the resulting artifacts into an [OCI image](https://github.com/opencontainers/image-spec).
+The `lifecycle` orchestrates buildpacks, then assembles the resulting artifacts into an [OCI image](https://github.com/opencontainers/image-spec).
+It does its work in a series of distinct "phases".
 
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+
+## Build Phases
+
+An **image build** requires 5 lifecycle phases, as shown below:
+
+![lifecycle phases](/images/lifecycle-phases.png)
+
+> **Note**: when talking about lifecycle phases you'll sometimes see nouns like `analyzer` or `/cnb/lifecycle/analyzer`
+> and you'll sometimes see verbs like `analyze` or `analyze phase`.<br><br>
+> These are all more-or-less interchangeable: the nouns refer to the lifecycle binary and the verbs refer to the work that the lifecycle performs.
+
+The lifecycle must be run in a containerized environment (such as a Docker container or CI/CD system).
+
+The [`analyzer`][analyzer], [`restorer`][restorer], and [`exporter`][exporter] (shown in pink above)
+require access to an image repository - either an **OCI registry** or Docker-compliant **daemon** (such as Docker or Podman)
+in order to do their work.
+
+This means that either registry credentials or a Docker socket must be available in the container where the lifecycle phase is running.
+For security hardening, these phases run in separate containers to avoid exposing sensitive data to **buildpacks**.
+
+The [`detector`][detector] and [`builder`][builder] (shown in purple above)
+invoke buildpacks to do the work of determining which buildpacks are needed and
+transforming application source code into runnable artifacts (the real work of buildpacks!).
+For security hardening, both the lifecycle and buildpacks run as non-root users when doing this work.
+
+When a builder is [trusted][trusted builder], all 5 lifecycle phases can be run in the same container,
+and in this case the [`creator`][creator] binary is used to run all 5 lifecycle phases with a single command invocation.
+
+To coordinate between phases, the lifecycle outputs a series of configuration files which are part of the [Platform API specification][platform api].
+For the most part, platform operators do not need to be concerned with these files unless they are designing their own platform.
+
+## Diving Deeper
+
+Read on to learn more about each lifecycle phase, including phases not shown above.
+These include phases relating to [starting][launcher] or [rebasing][rebaser] the application, or [extending][extender] base images used during the build.
+
+[trusted builder]: /docs/for-platform-operators/how-to/integrate-ci/pack/concepts/trusted_builders
+[creator]: /docs/for-platform-operators/concepts/lifecycle/create
+[analyzer]: /docs/for-platform-operators/concepts/lifecycle/analyze
+[detector]: /docs/for-platform-operators/concepts/lifecycle/detect
+[restorer]: /docs/for-platform-operators/concepts/lifecycle/restore
+[builder]: /docs/for-platform-operators/concepts/lifecycle/build
+[exporter]: /docs/for-platform-operators/concepts/lifecycle/export
+[launcher]: /docs/for-platform-operators/concepts/lifecycle/launch
+[rebaser]: /docs/for-platform-operators/concepts/lifecycle/rebase
+[extender]: /docs/for-platform-operators/concepts/lifecycle/extend
+[platform api]: /docs/reference/spec/platform-api

content/docs/for-platform-operators/concepts/lifecycle/extend.md

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++++
+title="Extend"
+weight=9
++++
+
+The `extender` applies Dockerfiles output by image extensions to the build or runtime base image.
+
+<!--more-->
+
+### Exit Codes
+
+| Exit Code       | Result                              |
+|-----------------|-------------------------------------|
+| `0`             | Success                             |
+| `11`            | Platform API incompatibility error  |
+| `12`            | Buildpack API incompatibility error |
+| `1-10`, `13-19` | Generic lifecycle errors            |
+| `100-109`       | Extension-specific lifecycle errors |