Depending on your nationality you might need a visa to cross the border into the Netherlands or into the Schengen area (which comprises of many European countries). The entry visa applicable for stays over 90 days is called a provisional residence permit or MVV (from the Dutch term machtiging tot voorlopig verblijf).

You can read more information about the MVV on this website of the Dutch Ministry of Foreign Affairs. 

Purpose Of Stay
A provisional residence permit is always issued for one particular purpose of stay. Examples include “highly skilled migrant” or “scientific researcher under EC Directive 2016/801”. 

Application procedure
Your employer may need to apply for a provisional Residence Permit (MVV) for you. The employer submits an application both for an mvv and a residence permit at the same time.

The IND (Immigration services) assesses the application and notifies your employer/host of the outcome. When it has been granted, the Dutch embassy/consulate will be notified as well.

From that moment on you can collect your MVV from the Dutch embassy. To collect your MVV at the Dutch embassy or consulate you will often need to make an appointment.