A number of holsters are generally designed to present security to the handgun, protect retention, and ready for use. Holsters are normally made to be used for a single hand, allowing the [object to be removed and/or replaced] with the same hand. To be able to bring back the object to a holster one-handed, the holster have to be made from stiff piece that keep the form, so that the holster won't fail when the object is no longer inside to give it support.
Some other holsters may inserted inside a pocket, to affixed stability and protection to the handgun, keeping it securely reliable and accessible than if it were in the pocket alone.
Categories by technique in wearing

Kinds of Well known holsters like the Fobus holster:
“Outside the waistband” (OWB) or belt holsters are ofter used by police and army, and by citizens who handpick to open carry. Belt holsters and can be hidden in a long, jacket and shirt untucked.
“Inside the waistband” (IWB) holsters, which clip or attached to belt and allow one to holster the weapon securely inside the pants give the wearer the selection of shirt stucking over the firearm and holster.
“Shoulder holsters” consist of several straps connected in a manner the same with the backpack. Shoulder holsters are designed to arrange the handgun: 1. in a vertical position, with the barrel pointed usually on the ground; 2. in a straight up position, with the barrel pointed generally upward; 3. in a flat position, with the barrel pointed normally at the rear of the wearer.
The "belly band" holster is a big elastic belt with a built-in holster, mostly worn under an untucked shirt, to facilitate access. In order to remain in place, a belly band must be tremendously tight; this is usually uncomfortable - it is comparable to wearing a girdle.
“Pocket holsters” are used for enormously small items or weapons, similar to back up gun or a mousegun.
“Small of Back” holsters place the weapon directly over the midpoint of the back, letting for even heavy handguns to be used with quite a little printing. While both comfortable and stylish, accidentally the wearer fall onto the weapon (such as in a close quarters fight) awful injury of the spinal column (including paralysis) may occur.
“Groin holsters” put the handgun mostly under the waistline around the 12:00 position. No restrictions for movement of the body and such a few restrictions of clothing with this holster style.
“Thigh holsters” are a well know military and police-item that handle the pistol on the leg right where the hand generally dangles, making for a relatively-fast-draw.  Today, this is with a drop leg PALS grid with a modular holster enclosed.  Police and law enforcers affiliates and operatives wear these when a big vest makes belt carry unreasonable.
“Ankle holsters” offer excellent cover up and are used continually by police officers who wish to carry a secondary weapon to back up the main firearm.
“Chest holsters” can be connected to MOLLE well match vests and chest carriers. Like shoulder holsters, chest holsters are often easier to draw from than belt holsters when the operator is seated inside a vehicle.
Other, specific types of holsters are designed to be mounted inside briefcases, day planners, purses and filofaxes, or even articles of clothing.