The chair's role in a charity is often defined by a list of duties and responsibilities ascribed to the role. Perhaps the most important of these is to be accountable, because this is a starting place from which so much else follows.
Much less thought is given to the powers a chair can exercise in the fulfilment of the role. Some chairs take it for granted that they have the power to lead decision-making and take decisions between board meetings.
There are dangers in this approach, because the law is clear that all trustees are equal and it is the board collectively that has decision-making authority.
Chairs can be granted certain powers in the form of delegated authority. Such powers really should be agreed in writing, most frequently in an approved job description or in a board minute.
When things are going well these issues do not appear to matter, but it is when things are going well that they should be put in place, because it becomes so much more difficult once problems do start to arise.