This article starts out as a good overview for beginners, but gets into some factual errors starting from the double-action-only section.
DAO pistols do not usually have two reset points; that's a characteristic of the SIG DAK system not found on other pistols.
As for striker-fired pistols, they can be single-action, double-action, or the intermediate design Glock popularized. Hammer-fired guns can also be intermediate with the HK LEM system being a prominent example.