> ## Documentation Index
> Fetch the complete documentation index at: https://docs.allium.so/llms.txt
> Use this file to discover all available pages before exploring further.

# Overview

> Plain-English explanations of the onchain concepts behind Allium's data, and how Allium handles each of them.

Blockchain data carries assumptions that are obvious to crypto-native engineers and invisible to everyone else: blocks can be un-mined, a "token" means five different things depending on the chain, and a trade can be a pool swap or a resting limit order.

These pages explain the concepts you need to read Allium's data correctly, and state what Allium actually does about each one — how deep we wait before calling a block confirmed, how we correct reorged records, and which tables represent which onchain primitive.

Start here if you are new to onchain data. If you already know the concepts and want schemas, go straight to the [Data Catalog](/historical-data/overview) or the [Realtime API](/api/developer/overview).

## Blockchain fundamentals

<CardGroup cols={2}>
  <Card title="Consensus mechanisms" icon="network-wired" href="/guides/consensus">
    How chains agree on a single history, and why that shapes the data you get
  </Card>

  <Card title="Rollups and L2s" icon="layer-group" href="/guides/rollups">
    What a layer 2 is, what a sequencer does, and the data quirks that follow
  </Card>

  <Card title="Transaction finality" icon="lock" href="/guides/finality">
    When a transaction is irreversible, and Allium's confirmation depth per chain
  </Card>

  <Card title="Reorgs" icon="arrows-split-up-and-left" href="/guides/reorgs">
    What happens when a chain discards blocks, and how Allium corrects for it
  </Card>
</CardGroup>

## Tokens and wallets

<CardGroup cols={3}>
  <Card title="Fungible vs non-fungible" icon="coins" href="/guides/fungible-vs-non-fungible">
    The difference between interchangeable and unique assets
  </Card>

  <Card title="Token standards" icon="list-check" href="/guides/token-standards">
    ERC-20, ERC-721, SPL, Token-2022, and why the differences matter for data
  </Card>

  <Card title="Hot vs cold wallets" icon="wallet" href="/guides/wallets">
    Custody models, and what each looks like onchain
  </Card>
</CardGroup>

## Trading and DeFi

<CardGroup cols={2}>
  <Card title="AMMs vs CLOBs" icon="arrows-retweet" href="/guides/amms-vs-clobs">
    Two ways to match trades onchain, and the two shapes of data they produce
  </Card>

  <Card title="Perpetuals" icon="chart-candlestick" href="/guides/perpetuals">
    Funding rates, leverage, liquidations, and the tables that track them
  </Card>

  <Card title="Oracles" icon="satellite-dish" href="/guides/oracles">
    How offchain prices reach onchain contracts, and how Allium prices assets
  </Card>

  <Card title="MEV" icon="robot" href="/guides/mev">
    Why transaction ordering has value, and how it distorts naive metrics
  </Card>
</CardGroup>

## Need something else?

These pages cover concepts, not schemas. For table-level reference see the [Data Catalog](/historical-data/overview); for endpoint reference see the [Realtime API](/api/developer/overview). If a concept you need explained is missing, email [support@allium.so](mailto:support@allium.so).