EU Blue Card
The EU Blue Card[1] is a type of work visa offered by many EU countries. Whereas a typical work visa ties you to a specific employer and only grants you residency to the host country, the Blue Card allows you to effectively transfer your residence to another country if you are able to find a job in the new country.
There is an effort to harmonize the rules for getting a Blue Card in each country, but it is up to each country to define their own rules around Blue Card visas.
The Blue Card is typically valid for up to 3 years and can be renewed.