The significance of this event is that it is one of, if not, the first recorded public discussions of democratic principles, worldwide.
These debates were held to resolve disputes within the New Model Army, concerning: the extent of suffrage; the balance of power between the House of Commons vs the King and the Lords; an agreement on certain native rights, such as equality under the law.
We can't determine how many people attended the debates but those present included: Oliver Cromwell (the chair), Thomas Rainsborough, his brother William, Henry Ireton, Robert Everard, Edward Sexby, William Allen, John Wildman, Maximillian Petty, and William Clarke who recorded the debates.
The first day of the debates took place in St Marys Putney but subsequently the meetings were held at the nearby lodgings of Thomas Grosvenor, Quartermaster General of Foot. We can't determine where this was.