Many artists use a combination of blue and black pencils. The blue pencil is used to rough out the character or draw the basic structure of the character. The darker black pencil is then used to do the final drawing. Some artists then go over their own work with inks, but some pass that on to another artist.
The penciller is a key part of the comic creation process. Without the penciller, there will be no story to be told, no characters to jump off the page, no panel by panel action. If the writer of the comic is the brain and heart of the story, the penciller is the skeleton, flesh, and skin, giving life and action to ideas.
Get more information about what a penciller is in this profile of the penciller.