The IUCN categories
There are many different types of protected areas across the world. The IUCN (International Union for Conservation of Nature) has split them into six categories. Even though the IUCN call category II 'National Parks', the UKs national parks are actually in category V.
I. Strict Nature Reserve/Wilderness Area:
A protected area managed mainly for science or wilderness protection
Denali National Park and Preserve, USA.
© Frank Kovalchek
II. National Park:
A protected area managed mainly for ecosystem protection and recreation.
Mu Ko Ang Thong National Park, Thailand.
© Jason Ellsworth-Aults
III. Natural Monument:
A protected area managed mainly for conservation of specific, unique natural features.
Owachomo Bridge, Natural Bridges National Monument, USA.
© Paul Kelly
IV. Habitat/Species Management Area:
A protected area managed mainly to preserve specific species and to maintain habitats
Young Gator at Lake Woodruff Wildlife Refuge, USA.
© Andrea Westmoreland
V. Protected Landscape/Seascape:
A protected area managed mainly for landscape/seascape protection and recreation.
Cairngorms National Park, UK.
© Bruce McAdam