Spotters are fine round ended paint brushes for painting fine details. These brushes have very small hair counts and are good for working on faces on figures, or fine detailed lines and painting on furniture. They usually have shorter brush handles as they are used for close up work. Choose a spotter with a handle that allows you the most brush control.
Liners and Riggers are also brushes for fine lines, but liners and riggers usually have longer fibers, which may make them not quite as suitable for particular purposes with miniatures. The same is true of pin striping brushes.