'Blind contour drawing' is when contour drawing is done without looking at the paper AT ALL.

This helps train you to look more often at your subject than look at your paper.  Staring down at your paper while drawing can be a hard habit to break~

"Continuous line contour drawing' is a contour drawing done without picking your pencil off of the paper.  It is essentially done with one long line.  Continuous line contour drawings can be done 100% "blind" or not.

A "modified contour line drawing" allows you to look at your paper and pick up your pen, using multiple lines instead of one.  

Although not completely blind, the artist should only look at the paper 10% of the time, and at the object 90% of the time.  The artist only looks at the paper to place their pencil when they start a new line.

Contour drawings use no shading, but lighter and darker tonal areas can be "suggested" by varying line width and pressure.  Darker, thicker lines can be used in shadow areas, and lighter, thinner lines in lighter areas.

Cross contour lines are drawn lines which travel, as the name suggests, across the form. Cross contours follow the form of the surface area- using curved lines over curving or spherical planes, straight lines across flat surfaces, etc.