What is the difference between coroutineScope { launch { code } } and withContext(iODispatcher) { code } in the Architecture Sample by Google?

Code: https://github.com/android/architecture-samples/blob/main/app/src/main/java/com/example/android/architecture/blueprints/todoapp/data/source/DefaultTasksRepository.kt

Snippet from the above Code link:

    override suspend fun activateTask(taskId: String) {
        withContext(ioDispatcher) {
            (getTaskWithId(taskId) as? Success)?.let { it ->
                activateTask(it.data)
            }
        }
    }

    override suspend fun clearCompletedTasks() {
        coroutineScope {
            launch { tasksRemoteDataSource.clearCompletedTasks() }
            launch { tasksLocalDataSource.clearCompletedTasks() }
        }
    }

    override suspend fun deleteAllTasks() {
        withContext(ioDispatcher) {
            coroutineScope {
                launch { tasksRemoteDataSource.deleteAllTasks() }
                launch { tasksLocalDataSource.deleteAllTasks() }
            }
        }
    }

    override suspend fun deleteTask(taskId: String) {
        coroutineScope {
            launch { tasksRemoteDataSource.deleteTask(taskId) }
            launch { tasksLocalDataSource.deleteTask(taskId) }
        }
    }

When to use which one?

Sometimes the coroutineScope { launch { code } } is inside withContext(iODispatcher)!

When to use: coroutineScope { launch { code } }

When to use: withContext(iODispatcher)

When to use them nested: coroutineScope { launch { code } } is inside withContext(iODispatcher)