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

# CONCEPTS

- [Fees and Spread](https://docs.rollie.finance/concepts/fees-and-spread.md)
- [Keepers](https://docs.rollie.finance/concepts/keepers.md)
- [Open Interest](https://docs.rollie.finance/concepts/open-interest.md)