In this YouTube video by Guns & Accessories, the host presents the basics of how a handgun works. There are many types of guns and ammunition. The host explains how ammunition is classified by its diameter size, whether in the Standard or Metric systems. Then he carefully demonstrates how a standard gun operates while not firing with it.
The host puts very strong emphasis on safety, and begins by imploring the viewer to attend a gun class in person. A gun shop should be able to refer you to a class and practice range in your area. A special point is made near the end of the video about trigger discipline. Do not place your finger on the trigger until the split second you are ready to destroy something. Any other time, keep your finger outside the rim around the trigger.
I will share more videos in this series about gun safety and training. However these are just a starting point. If you purchase a gun, I urge you again to get in-person training. That way an instructor can advise you what type of gun is best suited for you, as well as catch errors in your technique.