Imagine you have two different train stations: one uses electric trains, the other uses diesel. There is no direct path between them. To transport passengers or cargo, you need to build a bridge that connects these two systems. In the crypto world, such a 'crossing' is called a blockchain bridge.
Why are they needed at all?
Different blockchains are like different universes: they have their own rules, tokens, and logic of operation. Bitcoin does not understand Ethereum smart contracts, and Solana does not interact directly with Avalanche. But it's important for users to be able to transfer assets or data between these networks. This is where bridges come into play.
How does it work?
The bridge takes your asset, for example, ETH, and 'locks' it in one blockchain. Then a 'mirror copy' of this asset is created on the second blockchain — a token that can be used in another ecosystem. When you want to return the asset, the copy is burned, and the original is unlocked.
Example:
You have ETH, but you want to use it on the Polygon network. The Polygon bridge takes your ETH, locks it on Ethereum, and gives you an equivalent on the Polygon network — Wrapped ETH (wETH).
What types of bridges are there?
Centralized — operate through a trusted intermediary.
Decentralized — managed by smart contracts or DAOs, more secure but harder to implement.
Risks:
Hacking bridges is one of the main pain points in DeFi. Hackers love bridges because they manage large amounts of money.
Losses from errors in smart contracts or network overload.
Conclusion:
Bridges are an important element of Web3 development. They allow different blockchains to 'talk' to each other and create a unified multi-network ecosystem. But just like any crossing — it's important to understand which bridge you are using and how safe it is.