The checkbox field is remarkably simple. Tap to select, tap again to de-select.
There is one thing you should be aware of: The checkbox can be manipulated in the Record List. This means you can select/deselect checkboxes without actually opening the record and saving it. This was added to make it easier to manage lists. If you do select/de-select a checkbox in a record list and you're either sorting or filtering (searching) on the checkbox, the record list will be updated automatically.