An Area Captain is a decision-maker and caretaker of an area.
As a decision-maker, they (as a group if more than one) decide how to allocate their budget, what tools/equipment/items are allowed in the area, and who is certified to use them. They can set policies for use of their area. They are the first-line decision-makers for an area, only overruled by a majority board vote.
As a caretaker, they keep an eye on the area to ensure it’s generally kept up, identify things that need to be fixed/sharpened/maintained, and if they don’t do it themselves they ask for assistance/funding to get it done. They either train or train other trainers to certify members using the tools. They consider the long-term budgetary needs as they review purchase requests. They respond to questions in their Slack channel and to the area’s email address. Whether online or in person, they are a visible presence for the area.
The amount of work varies by area, but in general an Area Captain should expect to contribute at least a few hours a week as an average. (There’s an ebb and flow. It’s OK to have lighter weeks as there are usually heavier weeks.)