Here is a brief summary....
Typically an artist is given a story and direction by the editor/writer. The artist (penciller) is then laying out the pages and doing the pencil work which can vary from being extremely detailed to fairly rough sketches.
The art then passes on to the next artist, the inker who puts pen, ink and brush work to the original pencils. Although the penciller is often considered as the primary artist the role of the inker is equally important and can’t be overlooked as their style may enhance or interfere with that of the penciller. From there the art is transformed into the comic book. Copies known as stats are made from the original art and shrunk in size since most of the original art piece are done on 11 by 14 inch pages.
If it is to be a color comic the stats are then colored by the colorist before being sent to the printer.
Overlays - Why and What for ? Also....what about the different colors the inker chooses, for example "red" lines ?
Let's start with the "Overlays". We have to remember that there were 4 printing plates generated based on the finished and inked art piece. One plate for red, one for yellow, one for blue and a black one.
So now imaginge a "white" looking effect in your comic book - how can they pull off a "white" effect ?
The answer is the overlays. Here I show an example - you will see where the rain drops were put on a separate overlay, the idea is that these rain drops "burn" through the 4 plates that get generated. And therefore leave the image white.