This term is actually a media creation than an official crime term. It refers to a robbery when the perpetrators enter the home with the intent of finding someone there. The perpetrators use weapons and (often) actual violence to get the people in the home to give them money, jewelry and other belongings. Household members in the home are often restrained, threatened and beaten, and they are often told that if they report the crime to the police, they will be killed.
This is a very scary type of occurrence. Thankfully, it is also extremely rare, which is why it gets so much media attention when it happens. If the perpetrators unlawfully enter the property, the crime is primarily a burglary. However, the introduction of guns or other dangerous weapons by the perpetrators, and the threat or use of those weapons, allow the crime to be charged as both burglary and robbery in many cases.
If weapons are used, there is a weapons enhancement added at sentencing (which means the suspects will do more time if convicted), and a firearms enhancement if a gun was used - an automatic 5 year additional sentence if convicted.