In case you want to bring any electrical appliances with you, here is the system The Netherlands uses: 230 volts and 50 Hz. It is a round pin attachment plug (see picture)
An adapter will allow you to plug an appliance designed for one type of outlet into another type of outlet. Despite the fact that more than a dozen different types of plugs are in use, a typical travel adapter kit usually contains about five adapters which are capable of dealing with most of the outlets shown here. Adapters often manage this versatility by bypassing the ground/earth wire.
Beware: an adapter by itself will not change the electrical voltage. You must be sure that your appliance can handle different voltages (either automatically or through a voltage switches). If it can't, you will need a voltage converter.
For 'grounded' plugs, the Schuko" plug and receptacle with side grounding contacts is used (see picture)
The receptacle will also accept the not-grounded plug shown in the previous tip.