Feature classes (vector data) and Rasters (raster data) are the main layer types used in ArcGIS. A feature class is a collection of objects (points, lines, or polygons) whose vertices are located according to a mathematical model of the surface of the Earth. The objects within a feature class are of a single type (e.g. points), and they are located according to a single coordinate system. (Mathieu Duvall, 2007 - Creating a Feature Class)
