In comic production, an inker is an artist who does the second phase of a page - inking the line art based on the artwork done by the penciller, i.e. drawing the final lines in black ink.
There is a great art to both pencilling and inking. Inking is much more than just tracing lines. The inker has to correct any flaws of the pencils, and has to make decisions on how to ink every line - in what thickness, straight or jittered, "dead" or "alive", etc. The inker also has to decide on light and shadow, on which parts of the panel are to be black or colorized later, etc.
Inking can be done with many different tools, such as pens, brushes, bamboo pens, markers, rapidographs, etc. The choice of tool will have an influence on
how the final inked drawing will look.
Inkers also work with other tools such as white-out or raster foil.
After the inking phase comes typesetting and colorization.