An excellent article and explanation about trigger actions:
concealednation.org
[BEGINNERS GUIDE] Single Action, DA/SA, or DAO: Which One Is Right For You? – Concealed Nation
One of the choices the beginning concealed carrier has to make is the type of firearm to carry. The majority choose the semi-automatic or auto-loading pistol, but there is a strong minority who favor the revolver. This decision, combined with the choice of round to be used, determines the type...
concealednation.org