What are the two categories of computer graphics software?

Answer 1

I can think of three: raster graphics, vector graphics and 3D graphics.

Raster graphics are composed of pixels, per say, dots of different values of red, green, blue and alpha (transparency value) or RBGA as it is usually called. It can also be cyan, magenta, yellow and black or CMYK.

Vector graphics are composed of vertexes and handles that control the the curvature of lines, this lines can be shown or used to describe color masses (shapes) which can have effects applied to them.

3D graphics have to mayor ways to describe the shapes. One is using vector graphics with an added depth coordinate value and then applying surfaces to the lines. The other one is placing vertexes in and then adding surfaces between them, usually between three or four (called polygons), but there can be more depending on the program. After the 3D shapes have been described, a 2D image can be mapped to it's surface.