What is the difference between a queue and a stream?

Thread - is the smallest unit of execution scheduling in an operating system. It represents a separate path of code execution.

Queue - is a data structure or, in the context of the Concurrency API, a mechanism for organizing and sequentially executing tasks (code blocks). The queue determines the order in which tasks are passed to a thread for execution.

Main differences:

Parameter	Thread	Queue
Object	Unit of code execution	Mechanism for organizing tasks
Resource	Requires system resources for creation/management	Is not a computational resource itself
Scheduling	Scheduled by the operating system	Determines the order of task dispatch to threads
Tasks	Executes one task at a time	Contains multiple tasks for execution
iOS/macOS	Low-level management (rarely directly)	High-level concurrency management (DispatchQueue, OperationQueue)

In iOS development, we often work with queues (e.g., DispatchQueue) or operations (OperationQueue) that abstract thread management. Queues place tasks in the correct order, and the thread management system (e.g., GCD) assigns them to available threads for execution.