Add Concepts page (#50)

* Add concepts.md

* copy update

docs/architecture.md

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 title: 🏛️ Architecture
 description: How Shorebird works.
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docs/concepts.md

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+---
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+title: 🎓 Concepts
+description: Concepts used in Shorebird's code push product
+---
+
+# Code Push Concepts
+
+An explanation of the concepts used in Shorebird's code push product.
+
+## Glossary
+
+### Application
+
+An application is what is created by running `flutter create [app_name]` and corresponds to a listing in the App Store or Play Store.
+
+Each application has a unique `app_id` that is assigned when you run `shorebird init`. You can find your application's id in the `shorebird.yaml` file at the root of your project.
+
+An application can have zero or more [releases](#release).
+
+:::note
+Applications that use build flavors will have a unique `app_id` for each flavor.
+:::
+
+### Release
+
+A release is a specific version of an [application](#application), identified by a version and build number (e.g. `1.0.0+1`). Although code push works for apps distributed outside of the App Store and Play Store, a release most often corresponds with a specific version of your app that is published to the App Store or Play Store.
+
+A release can have zero or more [patches](#patch) applied to it.
+
+Releases are created by running `shorebird release [platform]`, where `platform` is `android`, `aar`, or `ios` (coming soon).
+
+### Patch
+
+A patch is a change to a specific [release](#release), applied as an over-the-air update. For example, a patch could be a bug fix or a new feature. Multiple patches can be published for a given release, although only one patch can be active at a time. Patches are identified by their associated release version and a patch number, which is an auto-incrementing integer.
+
+When your application starts, it checks for available patches and applies the latest one. This patch will be visible the next time your application launches.
+
+Patches are created by running `shorebird patch [platform]`, where `platform` is `android`, `aar`, or `ios` (coming soon).
+
+### Artifact
+
+An artifact is the output of a build or patch operation. For example:
+
+- `shorebird release android` generates and uploads several architecture-specific `libapp.so` files and an Android archive (.aab) file. These are **release artifacts**.
+- `shorebird patch android` generates and uploads diff files that capture differences between your Dart code at patch time and the code in the associated release. These are **patch artifacts**.

docs/faq.md

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 title: ❓ FAQ
 description: Frequently asked questions.
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docs/status.md

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 title: 👷 Status
 description: Status of the Shorebird project.
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docs/uninstall.md

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 title: 🛑 Uninstall
 description: How to disable Shorebird.
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