# Key Terms * **Payment ID:** A human-readable identifier (like alice\@binance) that maps to multiple blockchain addresses across different sources and networks. * **ZK Email:** A privacy-preserving technology that uses zero-knowledge proofs to verify email ownership and content without revealing the actual email address on-chain, serving as the identity layer for Payment ID. * **Wallet:** A deterministic smart contract wallet derived from a user's email address using zero-knowledge proofs. Each email maps to exactly one wallet, providing a consistent on-chain identity while keeping the email private and enabling transaction execution through ephemeral session keys. * **PID Token:** An ERC-721 non-fungible token that represents ownership of a Payment ID, allowing for transfers and delegated management. * **Resolver:** A smart contract that maps Payment IDs to blockchain addresses based on the source context (exchange/wallet/anything) and blockchain network. * **Source Type:** An identifier for different sources of funds (exchanges, wallets, anything) that allows a single Payment ID to have different addresses for different contexts (e.g., @binance, @metamask, @mytopaccount). --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.space.id/payment-id/key-terms.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.