Depending on your nationality, entry conditions may apply. You may need to have an entry visa and/or a residence permit. If so, your Dutch host organisation will usually deal with a lot of the paperwork, especially when your stay in the Netherlands longer than 90 days.
Visa
A visa is a legal document allowing you to cross the border to The Netherlands and Schengen area. Your stay is limited to a maximum of 90 days.
Residence permit
When you are staying in the Netherlands for longer than 90 days and you do not have a European nationality, you probably need a residence permit in order to have legal stay. When you are scientific staff your host organisation will arrange the residence permit for you.
Additional information
Embassies - Legalisation - Family & immigration procedures - Pre-departure - Upon arrival