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

# Key concepts

- [Overview](https://developers.usetoggle.com/key-concepts/overview.md): Orders, Transactions, Line Items and more
- [Orders, Transactions & Line Items](https://developers.usetoggle.com/key-concepts/overview/orders-transactions-and-line-items.md): Some useful key structures and terms
- [Card number formats](https://developers.usetoggle.com/key-concepts/overview/card-numbers.md)
- [Tender vs Discount](https://developers.usetoggle.com/key-concepts/overview/tender-vs-discount.md)