Contact sheets are sheets that display all of the photos you have taken. It is used to display the process and selection of images that you want to manipulate/publish. Naturally there are going to be photographs that are faulty/unappealing and contact sheets are a way of displaying the thought process behind which images are better and preffered over the others. Contact sheets are easy to produce and make  the photographer much more professional. Contact sheets are also a way of pre showing what you want to do to the image and how you want to manipulate. You can perform certain symbols and use certain colours which will symbolise particular methods of manipulation. Here are some examples of some other photographers contact sheets:

Here is an example of one of my contact sheets:

Green circle - An image I would like to further use.

Red cross - An image I would not like to use.

Red F - The image is out of focus.

Red shading - The part of the image I would like to crop out.

Yellow question mark: An image I am unsure whether to edit or not.