Second Strike...

Only true double action designs have “Second Strike” capability. If, when the trigger is pulled, the primer fails to go off, second strike capability provides an additional opportunity to fire the cartridge. This is most useful in cases where there is a defective, high, or unusually hard primer. In the case where the primer is not fully seated, the first strike of the firing pin will often seat the primer allowing the second strike to successfully fire the cartridge. Much like a piñata, a stubborn primer will sometimes require a second whack as well, and of those that fail to go off the first time, tests have shown that 80% will touch off the second attempt.
Many will of course argue that the proper procedure to follow after hearing an un-expected “click” is the “tap, rack, bang”. (make sure the magazine is properly seated, cycle a fresh round into the cham-ber, pull the trigger again) The fortunate few among us with the opportunity to shoot 10,000 + rounds per year in training including a focus on failure drills, may remember to do this under stress. The rest of us will more often than not, continue to pull the trigger at least one more time after a failure.
All of the DA/SA handguns in the CZ line have second strike capability including the 75, 83, P, and SP series.