There are the Public Seminars, which as the name implies are open to the general public. There is often a fee for attending one of these (but not always), and they can last from a couple of hours to all day. These are usually advertised in the locality and on the web, well in advance of the dates. These meetings also tend to be themed.
Meetings are usually conducted at the invitation of a private club, such as the Rotary, Lions, Women's Institute, Village or Church Clubs and the like. Generally these are only open to the members of the club or organisation, according to their own rules.
Spirit in Business can be likened to a combination of the two meetings above, depending on demand. They can be an open meeting addressing some of the needs of business which anyone can attend (usually for an entrance fee), or they can at the behest of a particular business.
