A safety switch was a feature of the NN-14 blaster pistol.
A safety mechanism was a feature found on certain firearms, preventing accidental firing.
Zare Leonis was invited into the Commandant's Cadets, a clandestine group at the Arkanis Academy. To prove himself, he was told to kill Penn Zarang, a cadet who wasn't performing well. The plan was for him to shoot the cadet during a training drill, making it look like an accident. To help with this, he received an E-11 medium blaster rifle and instructions to cycle the weapon's safety three times to enable full-power shots.
Han Solo gave Rey an NN-14 blaster pistol, which included a safety. When she tried to use it against Unkar Plutt and his henchmen, it didn't work because she hadn't turned off the safety, something she didn't know about. Later, she disengaged it before using the blaster against First Order stormtroopers.
In Star Wars: The Force Awakens, Rey is depicted taking the safety off her blaster before she shoots at stormtroopers. The novelization of the movie adds context by showing Rey's attempt to use the blaster against Unkar Plutt, which failed because the safety was on. This scene was also cut from the final film, but appears as a deleted scene.