"They are at my place."
Translation:De er hjemme hos meg.
'Hos' doesn't have a precise English translation - it's similar to 'chez' in French, if that helps? So 'de er hos meg' is like 'they are at my place', while 'de er hjemme hos meg' is just giving more emphasis to the idea that they are at your home, specifically. The reason you might need to do this is you can also use 'hos' in front of certain professions, e.g. "I morgen har jeg en avtale hos legen" - tomorrow I have an appointment at the doctor's.