Oracle
An oracle delivers off-chain information, such as prices or events, to a blockchain application.
Category
On-Chain Data Plumbing
These terms describe data feeds, chain indexing, query layers, and raw event records.
How to recognize this theme
Terms that help apps read blockchain activity and external price data.
In a daily board, this category groups terms by their shared role. Look for four cards that describe the same mechanism, risk area, or workflow rather than four words that merely sound similar.
Educational context
These entries are vocabulary notes for learning. They are not project endorsements, token recommendations, exchange rankings, or trading signals.
Indexer
An indexer processes blockchain data into a form that is faster to search and query.
Subgraph
A subgraph is a structured way to define and query indexed blockchain data, often through a Graph-style API.
Event Log
An event log is a record emitted by a smart contract that can be indexed and searched later.