Function
Each of the 50 states in the U.S. has laws that allow most citizens, usually over the age of 18 who have not been convicted of a felony, to legally own or carry certain weapons that can be used for self defense in the event of an assault. Legally sanctioned self defense weapons are only covered by state and federal laws for the purpose of fending off an attacker or preventing a felony that is either in progress or is going to occur immediately.
Features
Self defense weapons are generally concealed in a purse, handbag, pocket, or belt and are meant to be pulled out quickly to either dissuade an attacker or fend off an attack already occurring. Some are only capable of disabling an attacker so that you can get away but most are capable of deadly force.
Types
Weapons used for self defense come in many sizes and have many different capabilities. Handguns are the most popular type of concealed weapon, but you may want to acquire something that is less deadly or has less of a chance of being used improperly. Many states allow the sale of electrical shock tasers for immobilizing an attacker as well pepper spray and even blunt objects such as batons. A few states allow the use of sharp weapons like knives and throwing stars.
Considerations
Each state has different laws governing the ownership and use of self defense weapons and not all states allow every type of weapon to be used. Check with your local law enforcement office or legal counsel before purchasing any sort of weapon. Some weapons, such as handguns or knives, will also require that you apply for a permit to be able to legally carry them. Many weapons that are legal to carry may not actually be practical for self defense such as throwing stars or nun chucks.
Warning
Take lessons in the proper use and concealment of any weapon that you are legally able to carry to help avoid any accidental discharge of a weapon. Be very careful when using a weapon for self defense as you can be arrested, fined, or even imprisoned if a court decides that you used the weapon outside of the boundaries of the law. Never use a self defense weapon to threaten anyone or harm someone who is not actively committing a felony.