# The network (/docs/concepts/network)

Bittensor is a blockchain (the **subtensor** chain) that coordinates and pays
for useful work. The work itself happens off-chain, inside **subnets**; the
chain records who participates, measures agreement about who is doing good
work, and emits the network's token, **TAO**, accordingly. The chain produces
one block every 12 seconds.

Subtensor is a Substrate-based chain. Each block contains **extrinsics** —
the submitted calls — and **events**; some events are emitted by the chain's
own per-block hooks (emissions, epoch boundaries) rather than by any
extrinsic.

## Networks and endpoints [#networks-and-endpoints]

The SDK's network names resolve to public endpoints:

* `finney` — mainnet, `wss://entrypoint-finney.opentensor.ai:443`
* `test` — public testnet, `wss://test.finney.opentensor.ai:443`
* `local` — a dev node at `ws://127.0.0.1:9944`

Mainnet also has a public **lite** node at
`wss://lite.chain.opentensor.ai:443` and an **archive** node at
`wss://archive.chain.opentensor.ai:443`. A lite node keeps only recent
state; to query state older than roughly 300 blocks (block-pinned reads,
historical snapshots) you need the archive endpoint or your own archive
node. Any `ws://` / `wss://` endpoint can be passed to
[`Client`](/docs/concepts/client) directly.

## Subnets [#subnets]

A subnet is an independent incentive market, identified by an integer
**netuid**. Each subnet has:

* an **owner** — the coldkey that registered it, who defines the incentive
  mechanism and sets its [hyperparameters](/docs/tx/set-hyperparameter);
* **miners** — hotkeys registered on the subnet that produce whatever the
  subnet's mechanism demands (inference, storage, predictions, ...);
* **validators** — hotkeys with enough stake behind them to hold a validator
  permit; they score miners by [setting weights](/docs/tx/set-weights);
* a liquidity pool pairing TAO with the subnet's own token, **alpha**.

Netuid 0 is the **root network**: it has no miners, no alpha token, and no
validation work — it is the pool where TAO is staked directly. Root TAO
stake counts toward validator stake weight on every subnet (see below) and
earns a share of each subnet's dividends. Registration there is stake-based
rather than burn-based; the root network's governance role is covered in the
[governance guide](/docs/guides/governance). By convention, root (TAO) is
priced at 1.0 wherever subnet prices are summed.

Subnet slots are limited: a subnet holds at most `max_allowed_uids` neurons
(default 256, and no lower than 64). Registering on a full subnet
([`burned-register`](/docs/tx/burned-register)) evicts the lowest-ranked
non-immune neuron; a freshly registered neuron is protected for an immunity
period, then competes like everyone else.

A neuron's **stake weight** on a subnet is
`alpha_stake + tao_stake × tao_weight` — its alpha staked there, plus its
root TAO stake scaled by the global TAO weight (currently 0.18 on mainnet,
governance-set). Validator
permits go to the top neurons by stake weight, up to the subnet's
`max_allowed_validators` (default 128), recalculated every epoch.

## TAO and alpha [#tao-and-alpha]

TAO is the chain's native token (1 TAO = 10⁹ rao). Each subnet also has its own
token, alpha, traded against TAO in the subnet's pool. Staking TAO into a
subnet swaps it to that subnet's alpha at the pool price; unstaking swaps back.
Alpha on one subnet is not worth alpha on another — the SDK's
[`Balance` type](/docs/concepts/money) enforces this at the type level.

Spot prices come from the [`alpha-price`](/docs/query/alpha-price) read, and
[`quote-stake`](/docs/query/quote-stake) / [`quote-unstake`](/docs/query/quote-unstake)
simulate a swap including fees and slippage before you commit.

## Emissions and epochs [#emissions-and-epochs]

The chain continuously emits TAO to subnets, and within each subnet to its
participants, in proportion to measured value. Each subnet runs on a cycle (its
**tempo**): validators submit weights over miners during the epoch, and at the
epoch boundary Yuma Consensus combines those weights — weighted by validator
stake — into ranks, trust, and incentive, which set each participant's share of
the emission. Delegated stake earns a share of its validator's dividends, minus
the validator's [take](/docs/tx/set-take).

The numbers behind all of this — halving schedules, the emission-share
formula, the 18/41/41 per-tempo split, and the consensus math — are on the
[Emissions](/docs/concepts/emissions) page.

The [`epoch-status`](/docs/query/epoch-status) and
[`blocks-until-next-epoch`](/docs/query/blocks-until-next-epoch) reads expose
the timing; [`metagraph`](/docs/query/metagraph) returns the full per-neuron
state of a subnet in one call.

## Who signs what [#who-signs-what]

Every account is an **ss58 address** backed by a keypair. Operations divide by
signer:

* **coldkey** — owns funds: transfers, staking, registration, subnet ownership.
* **hotkey** — operates on subnets: weights, serving an axon.

The [wallets page](/docs/concepts/wallets) covers how the two keys relate and
how to manage them.