All types of handguns have sights and actions, and they may have safeties or magazines.
In semi-automatic handguns, the magazine is the place where the cartridges are stored. It is a removable, spring-powered ammunition storage and feeding device that is inserted into a semi-automatic handgun. When you work the action, a cartridge is picked up from the magazine and placed in the chamber ready to be fired.
Magazines are designed with a spring and follower that push against the cartridges to move them into the action. When checking a magazine to make sure it's empty, you must be able to see and feel the follower; if you cannot see or feel the follower, there may be a cartridge jammed in the magazine, which can be dangerous.