What are the types of blockchain?

Blockchain technology is essentially a distributed ledger and can be implemented in different types. Here are some of the commonly used types of blockchain:

1. **Public Blockchain:**
Public blockchains operate in a publicly accessible manner, where any user can join the network and verify transactions. Cryptocurrencies such as Bitcoin and Ethereum are popular examples of public blockchains.

2. **Private Blockchain:**
Private blockchains have a structure where participants and transactions are limited and usually controlled by an organization or entity. Such blockchains can be used to keep transactions private or facilitate the sharing of information among a specific group of people.

3. **Consortium Blockchain (Consortium Blockchain):**
 Consortium blockchains represent a structure that is shared and requires collaboration between several organizations or groups of organizations. Participants usually follow a specific agreement or protocol and work together to verify and record transactions.

4. **Hybrid Blockchain:**
 Hybrid blockchain represents the combination of public and private blockchain models. It maintains the privacy and control benefits of private blockchain while leveraging the transparency and accessibility of public blockchain for certain situations.

5. **Permissioned Blockchain:** Permissioned blockchains refer to a structure in which participants must join the network with certain permissions. Participants are typically identified through authentication or permissions associated with specific roles.

6. **Structured Blockchain (Permissioned Blockchain):**
 A structured blockchain is a permissioned structure created and managed by a specific consortium or organization. Participants are usually identified and verified and have a specific role or authority in the network.
Each type of blockchain is designed for different requirements and use cases and has different advantages and disadvantages. The type of blockchain to choose often depends on the needs and goals of a particular project or application.

7. **Smart Contract Blockchain:**
Smart contract blockchains support autonomous pieces of software known as smart contracts. These types of blockchains use programmable contracts that enable transactions to be processed automatically. Platforms such as Ethereum are popular examples of blockchains where smart contracts are implemented.

8. **Mutable Blockchain:**
Exchangeable blockchains have a structure that is under a certain central authority or control and where data can be changed when necessary. These types of blockchains are typically managed by centralized organizations or governments and are designed to meet users' security or regulatory requirements.

9. **Immutable Blockchain:**
 Immutable blockchains have a structure in which data, once recorded, is irreversibly unchangeable. Such blockchains are often used to support secure and transparent transactions such as cryptocurrencies.
10. **High-Performance Blockchain:**
High-performance blockchains are designed to provide fast processing speeds, low costs, and scalability. These types of blockchains are especially used in areas with high-volume transaction requirements, such as financial transactions or enterprise applications.

11. **Energy-Efficient Blockchain:**
 Energy efficient blockchains are designed to reduce the direct energy consumption of mining or transactions. Such blockchains are becoming increasingly important for reducing environmental impacts and ensuring sustainability.

12. **Cross-Chain Blockchain:**
 Cross-chain blockchains have a structure that enables interaction or facilitates data transfer between different blockchain networks. These types of blockchains are used for applications that require asset transfer, data sharing, or collaboration between different platforms.

Each type of blockchain is designed for a specific use case or need and has different features and benefits. The type of blockchain to be implemented is chosen depending on the project's objectives, security and performance requirements, participants' needs, and other factors.