6) Line as Value

Some ways that an artist could use line to show value would be to hatch which is drawing lines that follow one direction.

You can see that this drawing usses only single direction lines to show value.

Cross hatching is a way to show heavier shading that is used when drawing the darker parts of a shadow and it consists of lines going in multiple directions.

You can see that this drawing uses lines that go in one direction to show value and as those values get darker there are lines going in multiple directions layed over each other.

5) Gesture line

Gesture lines are used to show the body of the object rather than like contour lines which show an outline.

The photo above is recognizably a person even though it is just lines and there is no definite outline.

Gesture lines are excellent for quickly sketching and showing motion.

You can see very much that this character is moving or dancing.

4) Contour line

Contour lines are a line that shows the outline of a form and gives a very general shape for people to recognize.

For instance everyone would recognize this as a pair of shoes even though it is just an outline with very little detail being shown.

3) Line as Emotion

Line can be used to convey emotion just like in this drawing by Louisa Gifford

The hair is used to show fury and anger as it flies away from the character's face.

2) Line Direction

Line can show direction in many ways.
For instance the photo below shows a line that draws your eyes towards the background by making your eyes follow it.

The photo bellow shows an implied line that makes you look for what it is that the gestured character is  picking up.

"Ooo used chewing gum!"

Psychic lines are lines that show direction by using something as small as the direction that a character is looking or pointing. Such as in this Caravagio below.

"Do it. You won't do it."

1) Line as Shape

Line can Have a very simple look

or it can show shape, for instance the shape below is a simple line but it creates a shape that we, as humans, recognize as a seal

Its actually a whale.



Space

This is a perfect example of space, it shows how things get smaller as they go further back in space. when items move in a strait line in space they can reach a horizon line and or create a vanishing point.