xecution may be immediate as in a synchronous callback, or it might happen at a later point in t

function .mw-parser-output .monospaced{font-family:monospace,monospace}main), deferred callbacks may be invoked after a function returns. Deferred callbacks are often used in the context of I/O operations or event handling, and are called by interrupts or by a different thread in case of multiple threads. Due to their nature, blocking callbacks can work without interrupts or multiple threads