# Foundational Concepts

- [Open-Source Software](https://energy-web-foundation.gitbook.io/energy-web-foundation/foundational-concepts/open-source-software.md)
- [Scaling Access to Grid Flexibility](https://energy-web-foundation.gitbook.io/energy-web-foundation/foundational-concepts/scaling-access-to-grid-flexibility.md)
- [Facilitating Clean Energy Purchases](https://energy-web-foundation.gitbook.io/energy-web-foundation/foundational-concepts/facilitating-clean-energy-purchases.md)
- [Ethereum](https://energy-web-foundation.gitbook.io/energy-web-foundation/foundational-concepts/ethereum.md): Foundational blockchain technology
- [Transactions and Transaction Costs](https://energy-web-foundation.gitbook.io/energy-web-foundation/foundational-concepts/ethereum/transaction-costs.md)
- [Self-Sovereign-Identity](https://energy-web-foundation.gitbook.io/energy-web-foundation/foundational-concepts/self-sovereign-identity-introduction.md)
- [Self-Sovereign Use Case Interaction](https://energy-web-foundation.gitbook.io/energy-web-foundation/foundational-concepts/self-sovereign-identity-introduction/ssi-user-interaction.md)
- [Cryptocurrency Wallets](https://energy-web-foundation.gitbook.io/energy-web-foundation/foundational-concepts/wallets-and-exchanges.md)
- [Software cryptocurrency wallets](https://energy-web-foundation.gitbook.io/energy-web-foundation/foundational-concepts/wallets-and-exchanges/software-cryptocurrency-wallets.md)
- [Metamask](https://energy-web-foundation.gitbook.io/energy-web-foundation/foundational-concepts/wallets-and-exchanges/software-cryptocurrency-wallets/metamask.md)
- [Mycrypto wallet](https://energy-web-foundation.gitbook.io/energy-web-foundation/foundational-concepts/wallets-and-exchanges/software-cryptocurrency-wallets/mycrypto-wallet.md)
- [Hardware cryptocurrency wallets](https://energy-web-foundation.gitbook.io/energy-web-foundation/foundational-concepts/wallets-and-exchanges/hardware-cryptocurrency-wallets.md)
- [Hierarchical Deterministic (HD) Wallets](https://energy-web-foundation.gitbook.io/energy-web-foundation/foundational-concepts/wallets-and-exchanges/hierarchical-deterministic-hd-wallets.md)