A polygon mesh is basically a construct of vertices, faces, and edges that defines the shape of an object which are then rendered on the screen by one of the chosen renderers that Irrlicht provides:

You might already know that there are different file formats for storing mesh data, for example, OBJ, MD2, MD3, and so on. Irrlicht supports 15 different file formats out of the box, so you should not run into problems when exporting your own model. These formats are 3DS, B3D, BSP, IRRMESH, LMTS, LWO, OBJ, MD2, MD3, MS3D, MY3D, OGRE, PLY, STL, and the X file format. Frequently used file formats are explained later in this chapter.

If you want to import a format that Irrlicht doesn't support, you can always write your own mesh file loader by extending the IMeshLoader interface that Irrlicht has provided. And hopefully, you can contribute back to the community again by distributing your newly-created loader class for Irrlicht. It's always a good idea to involve...