# DOT - Polkadot

### Polkadot Architecture

* **Relay Chain (L0 protocol)** - heart chain, responsible for network security, consensus & cross-chain interoperability
* **Parachain (L1 chain)** -  sovereign blockchain, rely on Relay chain's validation power
* **Bridge** - bridge chain, allow Polkadot shards to communicate with external blockchain like Ethereum

### Parachain advantage

* **Flexibility** - customizable native token, fee structure & economy
* **Interoperability** - parachains are cross-chain composability, can communicate with each other
* **Scalability** - Polkadot enable parachains as individual blockchain, parachains are also capable to incorporate l2 solutions&#x20;
* **Security** - connect with Relay chain to shared its security



### Slot auctions & Crowdloans <a href="#parachain-slot-auctions-and-crowdloans" id="parachain-slot-auctions-and-crowdloans"></a>

* Parachains connect to Polkadot by leasing an open slot on the Relay Chain via auction
* invest in parachain projects you support to earn project tokens / rewards
* facilitate a community driven way to maintain the quality of new projects
* How auctions work
  * parachain teams lock up DOT tokens for the duration of the lease
  * locked DOT cannot be withdrawn during the lease, return all DOT token after the lease
  * prachain teams can coduct crowdloans to accept DOT contribution from supportors
  * lease ranging from 12-96 weeks
  * one parachain can be used by different projects given the lease is not overlapping
