Raster images consist of a rectangular grid of small squares or dots known as pixels
In CAD point of view Vector is a line defined by its end-points and nodes, as opposed to a line formed from a series of points on a bitmap.
A raster image is made up from pixels, like the picture from a scanner, or the screen image on a computer monitor. It has a finite amount of detail which is dependant upon the image size and resolution. The more coarse it appears when you look at a raster image closely. If you magnify a raster image the pixels just get bigger, and you don't see any extra detail. A vector image is stored as geometric objects, such as lines and arcs, which are drawn between specific coordinates. If you magnify a vector image you see the lines more accurately, and the line edges stay smooth. Vector drawings are utilised in CAD (Computer Aided Design) and GIS (Geographical Information Systems) and other applications where accuracy is important. A raster to vector converter translates a raster image into the corresponding vector image.
You can convert the raster image files into the vector file format and save the file in dxf file format to work in cad using Raster to Vector Converter in ActCAD.