Threading With Swift Concurrency and Coroutines

Concurrency lets work overlap in time. Parallelism means work actually executes at the same time. A responsive app needs clear rules for where work runs, who owns it, and how shared data changes.

Separate suspension from blocking

A suspending network API can pause a task without blocking the UI thread while it waits. A blocking API occupies its thread until the call returns.

The words async and suspend do not automatically move CPU work away from the UI. A long calculation or blocking file read can still run in the caller's execution context.