Choosing a Gun

What gun (or guns) do I need to defend myself or my family in my house?
Putting it simply, it is best to have a handgun AND a shotgun for home defense.
Shots from a pistol can stop an intruder but will require a certain skill level to hit the target. A pistol is easy to conceal in a bedside night table which can make it easy to find when needed.
Shots from a shot gun can stop one or more intruders because the multiple shot gun pellets spread out and can cover 6 inches to 1 foot circle making accuracy less difficult especially in a high stress event such as a home invasion. A shotgun can be 4 feet long and is more difficult to conceal and find when needed in your house.
Having both in your house gives you more options to defend yourself. You can keep the pistol in your bedside night table and the shotgun in a closet. Keeping them in different locations gives you access options because you don’t know where the intruder will enter your domain.

What is the difference between pistol bullets and shotgun shell sizes? How do I know what I want or need?
Let’s start with pistol caliber. The caliber is the diameter of a bullet in millimeters or fractions of an inch.
You might have heard a gun referred to as a 9mm, or a 22, 25, 380, 38, 40, 45 or a 50.
Putting it simply, the larger the bullet, the more stopping power you will have to defend yourself. A 22 caliber bullet is so small it may not be able to penetrate an intruder who is wearing multiple layers of clothing. It is not recommended to use 22 or a 25 for personal defense!
As for shotgun shells, the same rules apply meaning the bigger the better. Shotgun shells can be in what they call “gauges” which can be 410, 20 or 12. A 410 is the smallest gauge and 12 is the largest. Now here is where it gets a little complicated … shotgun shells can have a single piece of lead or can have numerous amounts of what they call “shot”. Shot is simply small round pieces of lead. If you have to shoot someone with a shotgun in a high stress environment, you’re better off using shells that have multiple small pellets versus one or two large ones. Using shells with a single or double pellets of shot will stop an intruder if your aim is great. Using shells with multiple but smaller pellets can still stop an intruder but will make aiming less critical.
The main drawback of using high caliber pistols and high gauge shotguns is recovery time. The shock you will feel after shooting the first large round can affect how accurate your second shot will be. This can more easily be overcome by practice in your yard or at a range.

In conclusion
These are the "general" rules for choosing guns for home self-defense ...
Pistol – .380 or higher
Shotgun – 20 gauge or higher

The most critical part of self defence shooting is knowing that you must shoot to kill. It sounds harsh and brutal but if you feel your life is in danger there is no point in trying to shoot the perpetrator in the arm or leg. Unless you're and expert marksperson trained in high stress environments, there is no reason to just wound the perpetrator. You will not know the perpetrator's capabilities after they are just wounded and in some cases you will only be able to get off one shot.