A niche is the role the animal has in the community.
What would happen if giraffes didn't exist?
If giraffes no longer existed the trees and the plants would overgrow
The giraffes few predators would have to find their meals somewhere else.
Certain birds are friends with giraffes because they eat the bugs off them and in return the giraffes become cleaner and healthier, so without giraffes those birds would go hungry.