Holiday homes are a luxury item known to remain empty for much of the year. For this reason they make an easy target for thieves. Because of this higher risk of being burgled, holiday homes are not insured in the same way as normal homes, and must be specified as such when you are buying the insurance.
If you have a holiday home and do not specify that it is not always occupied at the time of purchasing the insurance, then your insurance company may void a claim in the event of damage or burglary.