JSON RPC
In plain terms
A lightweight remote-procedure-call protocol using JSON.
Going deeper
JSON-RPC encodes method calls and responses as JSON, enabling simple remote procedure calls over various transports. It's a minimal RPC format.
Under the hood
Stateless and transport-agnostic; simpler than SOAP, with batch requests supported.
Examples
Blockchain APIs (Ethereum), microservices, simple RPC, bitcoin-cli.
Think of it like...
Like mailing a simple form that names the function to run and its arguments.