Challenging Terrain
Challenging terrain has exposure to well defined avalanche paths, start zones, or terrain traps. Options exist to reduce or eliminate exposure with careful route finding. Check out the slideshow for examples of challenging terrain:
This slope is steep enough to avalanche. Your group would want to stay well spread out here and practice good travel habits if you were to cross it.
Simon Horton 
This terrain features a mix of trees and open areas. These sparse trees border a more obvious avalanche path down the middle. But even in the trees there are terrain features that need to be carefully considered, especially with respect to wind loading.
Ian Tomm 
This area contains avalanche slopes, but there is high ground that provides options to avoid them.
James Floyer Travel in challenging terrain requires a more thoughtful approach, including a thorough assessment of conditions. Big slopes with serious consequences exist, so you will need good travel techniques to travel through them, and under some conditions they should be avoided entirely. There will be frequent points at which travel decisions will need to be made to manage risk based on the current conditions and options available.