> For the complete documentation index, see [llms.txt](https://docs.etherscale.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.etherscale.xyz/core-concepts.md).

# Core Concepts

- [Overview of Rollups](https://docs.etherscale.xyz/core-concepts/overview-of-rollups.md)
- [Optimistic Rollups](https://docs.etherscale.xyz/core-concepts/overview-of-rollups/optimistic-rollups.md)
- [ZK Rollups](https://docs.etherscale.xyz/core-concepts/overview-of-rollups/zk-rollups.md)
- [Spike in Rollup Adoption](https://docs.etherscale.xyz/core-concepts/overview-of-rollups/spike-in-rollup-adoption.md)
- [Rollup as a Service](https://docs.etherscale.xyz/core-concepts/rollup-as-a-service.md)
- [Existing Problems with RaaS](https://docs.etherscale.xyz/core-concepts/rollup-as-a-service/existing-problems-with-raas.md)
- [Needed Solutions for RaaS](https://docs.etherscale.xyz/core-concepts/rollup-as-a-service/needed-solutions-for-raas.md)
- [EtherScale's Approach](https://docs.etherscale.xyz/core-concepts/rollup-as-a-service/etherscales-approach.md)
- [Introduction to EigenLayer](https://docs.etherscale.xyz/core-concepts/introduction-to-eigenlayer.md)
- [What are ScaleApps?](https://docs.etherscale.xyz/core-concepts/what-are-scaleapps.md)