# Key concepts > The ideas the rest of these docs build on, from shares, share value and collateral to borrow venues, lending venues, loan-to-value, the spread and harvests. Source: https://app.tango.finance/docs/concepts The tango.finance docs use a small set of ideas again and again. This page explains each one in two or three sentences, so the rest of the docs are easier to follow. Each idea links to the page that covers it in depth. > **Key points** > > - You supply a stock and receive shares. Your shares are counted in that stock. > - The strategy posts the stock as collateral at borrow venues, borrows a stablecoin, and lends it at lending venues. > - The spread between lending income and borrowing cost is harvested into more of the stock. > - Roles decide who may change what. Changes that add risk wait behind the curator's delay. ## Tokenized stock A **tokenized stock** is a token on a blockchain network that tracks one share of a listed company, such as AAPL. Its issuer sets its rules, such as who may hold it and how corporate actions like splits are handled. On tango.finance you buy, hold and supply these tokens from your own wallet. ## Vault A **vault** is the smart contract that holds the stock people supply and runs the strategy on it. Each stock has its own, and it gives you shares for your part. See [Using a vault](https://app.tango.finance/docs/vault/overview.md). ## Shares and share value When you supply, you receive **shares**, a standard ERC-20 token. **Share value** is all the stock held divided by the number of shares, so a share is always worth a number of units of the stock. No price is read to work it out. See [How your stock compounds](https://app.tango.finance/docs/how-your-stock-compounds.md). ## Collateral **Collateral** is stock posted at a money market so the strategy can borrow against it. It still counts as part of the stock your shares stand for. If the money market liquidates part of it, less is counted. ## Borrow venue A **borrow venue** is one position at a money market where the stock is posted as collateral and a stablecoin is borrowed. The contract supports Morpho Blue markets and Aave v4 markets. See [Borrow venue support](https://app.tango.finance/docs/vault/borrow-venues.md). ## Lending venue A **lending venue** is a money market where the borrowed stablecoin is lent to earn interest. It is an ERC-4626 vault, a standard kind of contract, such as a Morpho vault. See [Lending venue support](https://app.tango.finance/docs/vault/lending-venues.md). ## Default stablecoin The **default stablecoin** is the stablecoin the strategy borrows and keeps its accounts in, such as USDC. The app shows each network's stablecoin by its own symbol. Other stablecoins can also be registered for lending. See [Asset support](https://app.tango.finance/docs/vault/assets.md). ## Loan-to-value and the liquidation line **Loan-to-value** (LTV) is the value of a position's debt divided by the value of its collateral. Each borrow venue sets a **liquidation line**, the LTV at which others may repay part of the debt and take collateral at a discount. The strategy borrows below that line to leave room for the price to move. ## Stablecoin book The **stablecoin book** is the strategy's stablecoin side: idle stablecoins and lending positions, less debt. It is kept apart from share value. A **surplus** is profit that can be harvested. A **deficit** means the book is short, and deposits and ordinary withdrawals stop until it is covered. ## Spread The **spread** is what the lending earns less what the borrowing costs. When it is positive, the stablecoin book grows. When it is negative, the book shrinks. See [How yield is generated](https://app.tango.finance/docs/how-yield-is-generated.md). ## Harvest and rebuy A **harvest** takes profit from the book, pays the performance fee, and buys more of the stock with the rest. A **rebuy** buys back stock that a liquidation took, using the surplus the liquidation left, without a fee. ## Idle stock and idle stablecoin **Idle stock** is supplied stock that is held rather than posted as collateral. Ordinary withdrawals pay from it. **Idle stablecoin** is stablecoin that is held rather than lent. ## Forced withdrawal A **forced withdrawal** pays a holder more than idle stock covers, by releasing collateral and repaying debt in the same transaction. Any holder can call it. See [Withdrawals](https://app.tango.finance/docs/vault/withdrawals.md#forced-withdrawals). ## Total APY **Total APY** is today's yearly rate from the money markets plus eligible rewards, after the performance fee, as a share of all supplied stock. It changes all the time. See [How yield is generated](https://app.tango.finance/docs/how-yield-is-generated.md#how-the-rates-on-a-stocks-page-are-measured). ## Roles and the curation service A **role** is the permission to change a set of the contract's settings or positions. The curator adds venues and stablecoins and sets fees, behind a delay. The operator runs positions day to day. On tango.finance an automated **curation service** holds the operator role. See [Profiles and access control](https://app.tango.finance/docs/vault/roles.md). ## Timelock A **timelock** is the wait between scheduling a change and making it. Changes that add risk, such as adding a venue or raising the fee, wait the curator's delay of at least three days. See [Timelocks](https://app.tango.finance/docs/vault/timelocks.md).