Tap the checkbox to complete a task. Depending on your checkmark settings, the task may be automatically archived as well.

You can also swipe right on the task to complete it.

To explicitly archive a task you can swipe left on the task and tap the More button.

Then choose the Archive option from the dropdown menu.

If you are viewing archived tasks you can tap the checkmark to re-open the task.

To move a task to the Trash swipe left on the task and tap the More button. Then choose the Move to trash option from the menu.

Right after you delete a task, you'll see a banner pop up at the bottom of the screen with an option to Undo in case you selected that option by mistake.