I am from the EEA or Switzerland
You do not need a visa to travel to the Netherlands. All nationals from the EEA and Switzerland can travel between member states freely. The EEA consists of the EU plus a number of other European countries. For a full list, see the Netherlands Worldwide website.
I am from a country outside the EEA or Switzerland
If you come to the Netherlands for 90 days or less, you will usually need a visa and a letter of invitation from the Dutch company you will visit. There must be information in this letter about why you are coming, and how long you will be staying. There is an online tool on the IND website where you can fill in your nationality to find out what you must do to get a short-stay visa. You can also download a form there, that Dutch companies can fill out instead of an invitation letter.
You can apply for a short-stay visa at the Dutch embassy or consulate in the country where you live. The visa, also called a type C visa, is a sticker in your passport. The short-stay visa is valid for 90 days. This can be a consecutive period, or a number of days. In any case, the visa is valid in the Schengen area for 90 days within a 180-day period. So, if you have stayed in the Netherlands for 90 days in a row, you cannot return for the next 90 days. This is also true if you have stayed in the Netherlands, Germany and France for 90 days in a row. Only after the 180-day period is over can you get a new short stay visa.
I am from a country outside the EEA or Switzerland, and I have a valid residence permit for an EEA country or Switzerland
You also will need a short-stay visa. You can apply for this at the Dutch embassy or consulate in the country where you live.
Stopover in a Dutch airport
Are you flying to the Netherlands, but only for a stopover on your way to and from a non-Schengen country? In that case, you may need an airport transit visa.