Hi, Knin,
Shading and highlighting are among the most basic necessities for nicely painted minis. It cannot be said what they are by describing the techniques used to do them, because \"putting thin lines\" and \"models darker or lighter on the sides\" can be used to achieve many things.
Take a look at the shirt (or whatever) you are wearing right now, there will be folds in the fabic. In the interior of the folds, the fabric will appear darker. This becomes shading. At the edges of the fabric and the outer edges of the folds, the fabric will appear lighter, and this becomes highlighting.
Take a look at yourself in a mirror. There will be brighter points on your skin, like on the tip of your nose or on your chin, because that\'s where the light is most likely to catch - yep, that\'s highlighting. Under your chin and under your nose, there will be darker patches where the light does not fall - shading.
These are just two basic examples of highlighting and shading in real life. Things do get more complicated if you think of a drinking glass or gems, but take a look at a few objects right now, and see where (and why) the brighter and darker spots on the objects are.
For examples of shading and highlighting on a mini, just browse through CMON. Anything with a score of 6 and higher should have decent shading and highlighting. Look at flesh and cloth in particular, and compare the examples to what you see in real life. Note how on minis the shading and highlighting are both emphasised - if we did things completely realistically, we\'d never notice the changes on such a small scale. Also, shading and highlighting are taken to their extremes in NMM (using non-metallic paints to paint metals) - an advanced technique.