Many are the circumstances and needs of the world. So, many are the kinds of secular institutes. There are only female institutes, which are the majority. Others are only made up of laymen, or include priests too. And finally, there are secular institutes that combine the three branches: laymen, laywomen and priests.
As for their lifestyles, many members of secular institutes live with their families or alone. Others form small groups of common life. Some secular institutes have their own apostolic works, while others reject them by rule. In short, there exists within these institutes a healthy and rich pluralism that the Church has always kept and defended.
The charisma of secular institutes expresses clearly some of the basic guidelines outlined by the Second Vatican Council: the universal call to holiness, the presence in the world to sanctify it from within, etc. "If they remain faithful to their vocation, they will be like an experimental laboratory in which the Church tests the concrete modes of its relations with the world" (Paul VI, March 25th, 1976).