nsIAccessible interface has several State Flags, Roles, Attributes and Methods. For now we are primarily interested in attributes accName, accRole, accState, accValue, accFocused, accNumActions and methods acccTakeFocus(), getAccActionName() and accDoAction().
accName returns the "name" of the accessible node, for example the name of the button, check box or menu item.
accRole returns a value representing what this accessible node is used for, for example, is it a link, static text, editable text, a check box, etc.
accState returns a value representing possible on/off states, such as focused, focussable, selected, selectable, etc.
accValue returns the "value" of the accessible node, such as URL for a link, the text a user entered in a field.
accFocused returns the accessible node which is currently focused.
accNumActions returns the number of actions that can be performed on the accessible node.
accTakeFocus method is used to get focus on to specified accessible node.
getAccActionName method returns the name of the action when you supply to it the action value. Eg. for buttons it returns "Press".
accDoAction performs the action specified on the accessible node. Eg. presses button for button node.