docs(README): Create Polaris-Core README (#2585)

* docs(README): Create Polaris-Core README

Author: adam-christian-software

README.md

@@ -42,11 +42,11 @@ Click [here](https://polaris.apache.org/in-dev/unreleased/) for a quick overview
 ## Quickstart
 Click [here](https://polaris.apache.org/in-dev/unreleased/getting-started/install-dependencies/) for the quickstart experience, which will help you set up a Polaris instance locally or on any supported cloud provider.
 
-## Building and Running 
+## Project Structure
 
 Apache Polaris is organized into the following modules:
 
-- `polaris-core` - The main Polaris entity definitions and core business logic
+- [`polaris-core`](./polaris-core/README.md) - The main Polaris entity definitions and core business logic
 - API modules (implementing the Iceberg REST API and Polaris management API):
   - `polaris-api-management-model` - The Polaris management model
   - `polaris-api-management-service` - The Polaris management service
@@ -59,7 +59,9 @@ Apache Polaris is organized into the following modules:
 - Persistence modules:
   - `polaris-eclipselink` - The Eclipselink implementation of the MetaStoreManager interface
   - `polaris-relational-jdbc` - The JDBC implementation of BasePersistence to be used via AtomicMetaStoreManager
- 
+
+## Building and Running
+
 Apache Polaris is built using Gradle with Java 21+ and Docker 27+.
 
 - `./gradlew build` - To build and run tests. Make sure Docker is running, as the integration tests depend on it.

polaris-core/README.md

@@ -0,0 +1,51 @@
+<!--
+  Licensed to the Apache Software Foundation (ASF) under one
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+  "License"); you may not use this file except in compliance
+  with the License.  You may obtain a copy of the License at
+ 
+   http://www.apache.org/licenses/LICENSE-2.0
+ 
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+  KIND, either express or implied.  See the License for the
+  specific language governing permissions and limitations
+  under the License.
+-->
+
+# Polaris-Core Module
+
+The `polaris-core` module contains the fundamental entity definitions, core business logic, and foundational interfaces that power Apache Polaris.
+
+## Overview
+
+`polaris-core` handles:
+- Entity Management
+- Security & Access Control
+- Common Persistence Logic
+- Object Storage Integration
+
+## Key Components
+
+### Entity Management
+Polaris has several different entities defined in `PolarisEntityType`. You can find their definitions in the package `org.apache.polaris.core.entity`.
+
+### Security & Access Control
+Polaris uses a role-based access control (RBAC) model. `PolarisPrivilege` defines the available privileges. The RBAC model is implemented in `PolarisAuthorizer`. For more information on authorization, see the package `org.apache.polaris.core.auth`.
+
+### Common Persistence Logic
+To store entities, Polaris provides a persistence layer built upon the `BasePersistence` interface. Common persistence logic is handled in the `org.apache.polaris.core.persistence` package. Implementations are found within [the persistence folder](../persistence).
+
+### Object Storage Integration
+Polaris supports multiple object storage providers. `PolarisStorageIntegration` provides an interface for accessing and managing data in object stores. For more information, see the package `org.apache.polaris.core.storage`.
+
+## Usage
+
+The `polaris-core` module is primarily consumed by:
+- **API Services** - Management and catalog REST services
+- **Runtime Components** - Server and admin tools
+- **Persistence Implementations** - Eclipselink, JDBC, etc.