In aderenza is friction climbing, exploiting the stickiness of the rubber compounds in climbing shoes. It's particularly used on slabs where there are few if any irregularities in the rock that would allow handholds.

http://getoutdoors.wordpress.com/2008/10/30/the-granite-dome...

Strapiombi are overhangs where the wall of the rock leans out beyond 90°. More weight is taken on the arms and the upper body, and even if you find footholds (not always), you struggle to hold your legs angled inwards onto the rock.

http://www.trails.com/list_1328_overhang-climbing-tips.html