An inside the waistband holster (IWB) is a holster that is worn inside the waistband of pants or shorts, typically concealed by a shirt or jacket. IWB holsters are popular for concealed carry because they allow the wearer to carry a firearm without it being visible to others.
IWB holsters come in a variety of materials, including leather, Kydex, and nylon. They also come in a variety of designs, including tuckable holsters, which can be tucked into the waistband, and non-tuckable holsters, which cannot. The best IWB holster for a particular person will depend on their individual needs and preferences.