docs: restructure introduction

Also fixed some links by moving the files.

docs/src/modules/ROOT/nav.adoc

@@ -1,10 +1,11 @@
-* xref:introduction/introduction.adoc[leveloffset=+1]
-* Quickstart
+* xref:introduction.adoc[leveloffset=+1]
+* Getting Started
 ** xref:quickstart/overview.adoc[leveloffset=+1]
 ** xref:quickstart/hello-world/hello-world-quickstart.adoc[leveloffset=+1]
 ** xref:quickstart/quarkus/quarkus-quickstart.adoc[leveloffset=+1]
 ** xref:quickstart/spring-boot/spring-boot-quickstart.adoc[leveloffset=+1]
 ** xref:quickstart/quarkus-vehicle-routing/quarkus-vehicle-routing-quickstart.adoc[leveloffset=+1]
+* xref:planning-ai-concepts.adoc[leveloffset=+1]
 * Using Timefold Solver
 ** xref:using-timefold-solver/overview.adoc[leveloffset=+1]
 ** xref:using-timefold-solver/configuration.adoc[leveloffset=+1]
@@ -32,4 +33,5 @@
 ** xref:upgrading-timefold-solver/overview.adoc[leveloffset=+1]
 ** xref:upgrading-timefold-solver/upgrade-to-latest-version.adoc[leveloffset=+1]
 ** xref:upgrading-timefold-solver/upgrade-from-optaplanner.adoc[leveloffset=+1]
+** xref:upgrading-timefold-solver/backwards-compatibility.adoc[leveloffset=+1]
 * xref:enterprise-edition/enterprise-edition.adoc[leveloffset=+1]

docs/src/modules/ROOT/pages/.index.adoc

@@ -18,13 +18,15 @@ ifndef::backend-pdf[]
 image::shared/timefold-logo.png[align="center"]
 endif::[]
 
-include::introduction/introduction.adoc[leveloffset=+1]
+include::introduction.adoc[leveloffset=+1]
 include::quickstart/.quickstart.adoc[leveloffset=+1]
+include::planning-ai-concepts.adoc[leveloffset=+1]
 include::using-timefold-solver/.using-timefold-solver.adoc[leveloffset=+1]
 include::constraints-and-score/.constraints-and-score.adoc[leveloffset=+1]
 include::optimization-algorithms/.optimization-algorithms.adoc[leveloffset=+1]
 include::responding-to-change/responding-to-change.adoc[leveloffset=+1]
 include::integration/integration.adoc[leveloffset=+1]
 include::design-patterns/design-patterns.adoc[leveloffset=+1]
+include::frequently-asked-questions.adoc[leveloffset=+1]
 include::upgrading-timefold-solver/.upgrading-timefold-solver.adoc[leveloffset=+1]
 include::enterprise-edition/enterprise-edition.adoc[leveloffset=+1]

docs/src/modules/ROOT/pages/frequently-asked-questions.adoc

@@ -0,0 +1,15 @@
+= FAQ
+:doctype: book
+:icons: font
+
+== How is Timefold Solver Licensed?
+
+Timefold Solver Community Edition is _open source_ software,
+released under http://www.apache.org/licenses/LICENSE-2.0.html[the Apache License 2.0].
+This license is very liberal and allows reuse for commercial purposes.
+Read http://www.apache.org/foundation/licence-FAQ.html#WhatDoesItMEAN[the layman's explanation].
+
+Timefold Solver Enterprise Edition is a commercial product
+that offers xref:enterprise-edition/enterprise-edition.adoc#enterpriseEditionFeatures[additional features]
+to scale out to very large datasets.
+To find out more, see xref:enterprise-edition/enterprise-edition.adoc[Enterprise Edition section] of this documentation.

docs/src/modules/ROOT/pages/introduction.adoc

@@ -0,0 +1,30 @@
+[#introduction]
+:page-aliases: ../index.adoc
+:doctype: book
+:sectnums:
+:icons: font
+
+[#whatIsTimefold]
+= What is Timefold Solver?
+
+Every organization faces planning problems: providing products or services with a limited set of _constrained_ resources (employees, assets, time, and money).
+Timefold Solver’s xref:planning-ai-concepts.adoc[PlanningAI] optimizes these problems to do more business with fewer resources using Constraint Satisfaction Programming.
+
+> Want to dive right into it? Follow our xref:quickstart/overview.adoc[Quickstart Example] to tackle your first planning problem in minutes.
+
+https://timefold.ai[Timefold Solver] is a lightweight, embeddable constraint satisfaction engine which optimizes planning problems.
+Example usecases include:
+
+.Timefold Solver's use cases include vehicle routing, employee scheduling, rostering, bin packing, and equipment scheduling.
+image::introduction/useCaseOverview.png[align="center"]
+
+Timefold Solver is 100% pure Java^TM^ and runs on Java {java-version} or higher.
+It xref:integration/integration.adoc#integration[integrates very easily] with other Java^TM^, Python, and other technologies.
+Timefold Solver works on any Java Virtual Machine and is compatible with the major JVM languages and all major platforms.
+It also supports Kotlin and Python.
+
+:!sectnums:
+== Next
+
+* Follow the xref:quickstart/overview.adoc[Quickstart Example] to tackle your first planning problem.
+* Learn about some important concepts used in the realm of xref:planning-ai-concepts.adoc[PlanningAI].