bridging basics

Author: jarrodwatts

docs/cdk/concepts/agglayer.md

@@ -1,9 +1,17 @@
 # Bridging
 
-[Bridges](https://ethereum.org/en/developers/docs/bridges/) are a fundamental component of L2s. They allow users to bridge funds from the L1 (Ethereum) seamlessly, to pay for gas fees or interact with dApps on the L2, and optionally bridge funds back to the L1.
+[Bridges](https://ethereum.org/en/developers/docs/bridges/) are a fundamental component of L2s. A core feature of chains built with the CDK is **interoperability**, which allows developers to access funds from Ethereum as well as other L2s when building dApps on your chain.
 
-CDK chains come with a built-in bridge service and customizable UI that enables users to move assets (both native and ERC20 tokens) between L1 and L2.
+## L1 <-> L2 Bridge
+
+CDK chains come with a built-in bridge service and customizable UI that enables users to move assets (both native and ERC20 tokens) between L1 and L2 or between different L2s.
 
 A key benefit to building ZK-powered L2s with the CDK is that there are no challenge periods unlike [optimistic rollups](./zk-vs-optimistic.md#optimistic-rollups), meaning users can move funds from the L2 to the L1 immediately after the [aggregation](./transaction-lifecycle.md#aggregated) process is complete (i.e. a ZK proof is posted & verified).
 
-![Bridge UI for CDK](../../img/cdk/bridge-ui.png)
+## Unified Bridge
+
+By default, chains launched using the CDK are opt-in to the AggLayer, enabling cross-chain transactions via the unified bridge. The unified bridge enables cross-chain L2 to L2 transactions to other chains that have opted-in to the [AggLayer](https://polygon.technology/blog/aggregated-blockchains-a-new-thesis).
+
+This allows developers to build unique cross-chain experiences by integrating a `bridgeAndCall` function into their smart contracts, enabling users to call smart contract functions on other L2 chains without requiring users to bridge or hold tokens on the target chain.
+
+Learn more on the [zkEVM unified bridge documentation](https://docs.polygon.technology/zkEVM/architecture/protocol/unified-LxLy/ulxly-rollupmanager/).

docs/cdk/concepts/bridging.md

@@ -63,8 +63,7 @@ nav:
         - Transaction Lifecycle: cdk/concepts/transaction-lifecycle.md
         - Transaction Finality: cdk/concepts/transaction-finality.md
         - Gas Fees: cdk/concepts/gas-fees.md
-        - Bridging: cdk/concepts/bridging.md
-        - AggLayer & Interoperability: cdk/concepts/agglayer.md
+        - Bridging & Interoperability: cdk/concepts/bridging.md
         - Admin Upgradeability: cdk/concepts/admin-upgradeability.md
       - Architecture:
         - CDK rollup: cdk/architecture/cdk-zkevm.md