---
title: Learn
url: https://stowly.dev/learn
description: Short explainers on the ideas behind AI costs.
docs_index: https://stowly.dev/llms.txt
version: v0.1
lastUpdated: 2026-09-19
---

> Fetch the complete documentation index at https://stowly.dev/llms.txt before exploring further.
# Learn

Short explainers on the ideas behind AI costs. No fluff, each one ends at the calculator.

## Articles

1. [What is a token?](https://stowly.dev/learn/what-is-a-token) — the chunk a model actually reads, and the unit you're billed in. ~4 min. Published 2026-09-19.
2. [What is prompt caching?](https://stowly.dev/learn/what-is-prompt-caching) — cache reads up to 90% cheaper, write premiums, short TTLs, and when caching pays off. ~4 min. Published 2026-09-19.