This is the House of Representatives. This is where its members have their meetings. Members are chosen during the elections by the Dutch people who are over 18. When your parents vote, they also choose who is going to govern the country. With all these votes, the political parties win 'seats'. The more votes, the more seats they get. And these 'seats' are basically these chairs.
The House of Representatives has 150 chairs. They are divided amongst the political parties. Someone who sits on such a chair for a political party is called a Member of Parliament. A Member of Parliament participates in the making of our laws. After the elections, it becomes clear how many seats each party has won and who will be in the House of Representatives.
But now it has to be decided which parties will form the 'government'. Parties that want govern together, must have half the number of seats plus one extra. Usually, one party will not succeed in winning that many seats. So parties will work together in a 'coalition'. The government is seated on this side of the House. The parties that form the government can also appoint the 'Ministers'. And each minister is responsible for specific issues that they have to manage. There is, for instance, a Minister of Education, there is one for Foreign Affairs, and one who manages all the money. The most important minister is the Prime Minister. He has to make sure that all the ministers do their work properly.