What is it?
LTV means loan-to-value. For each collateral asset, Aave publishes a maximum borrow percent. If ETH LTV is 80%, then $10,000 of ETH collateral can support at most $8,000 of new borrowing under that rule (other limits can still bind).
Why does it matter?
LTV caps how far a wallet can lever up. A lower LTV is a stricter borrowing limit. It is not the same as liquidation threshold.
Example
USDC might allow a high LTV because its price is stable. A volatile token often has a lower LTV so people cannot borrow as close to the edge.
Where can I find it?
Asset detail KPI LTV, and the reserve table on a Market page. Wallet views talk about current LTV in technical details when Aave reports it.