Most real world features can be presented as vector or raster layers. In open source world, GDAL provides a comprehensive set of tools to interact with such datasets. But vector or raster is not always a suitable description of real world features. Data from oceanography, metrology, hydrology, etc often have multiple components at each location on an irregular structured mesh.

A mesh can a collection of vertices, edges and faces in 2D or 3D space:
- vertices - XY(Z) points (in the layer's coordinate reference system)
- edges - connect pairs of vertices
- faces - sets of edges forming a closed shape - typically triangles or quadrilaterals (quads), rarely polygons with higher number of vertices