Materiality

The main example is anything required to be presented separately or disclosed in accordance with the applicable financial reporting framework. For example, in the UK, there are extensive disclosure requirements for transactions with directors (e.g. loans), salaries and number of employees. It does not matter that these things are not material by size (an in the case of the # of employees it is not even a monetary amount) – they are material “by nature” because they can and should be stated accurately.
Something like cash at bank may be described as material by nature because even though the amount may not be material it is one of the few balances that is capable of precise measurement (similarly share capital) – it is not estimated – so the auditor should have not tolerance for misstatements in these amounts.