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description: Enabling interactions and token transfers between chains
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# What is Bridging？

### What is a "Bridge"?

App developers and users commonly need to move data and assets between Layer 1 (L1) and Layer 2 (L2). We call the process of moving data and assets between the two networks "bridging".&#x20;

Here is a good explanation of bridging from [Ethereum Documentation](https://ethereum.org/en/bridges/):

`"Bridges work just like the bridges we know in the physical world. Just as a physical bridge connects two physical locations, a blockchain bridge connects two blockchain ecosystems. Bridges facilitate communication between blockchains through the transfer of information and assets.`

`Let's consider an example:`

`You're from the USA and are planning a trip to Europe. You have USD, but you need EUR to spend. To exchange your USD for EUR you can use a currency exchange for a small fee."`

### **Why Do We Need a Bridge?**&#x20;

United Protocol (L2) is a separate blockchain system from Ethereum (L1). Similar to exchanging USD for EUR, we need a way to move **$ETH** and other tokens from Ethereum to United Protocol so the blockchain system will recognize and accept it in a verifiable and secure way.&#x20;

In order to move assets into or out of United Protocol network you can use the United Protocol Bridge.&#x20;

**For deeper explanations on bridging we encourage you to explore the following resources (external links):**

* [Blockchain Bridges](https://ethereum.org/en/bridges/)&#x20;
* [Ethereum Developer Docs - Bridges](https://ethereum.org/en/developers/docs/bridges/)&#x20;
