The food chain from leaves to humans may be a bigger part of the food web that includes not only the humans, but also other predatory animals and grazing animals, as well as other autotrophic varieties. Food web incorporates all these to see the connections between each of them.
The wolf is at the top of the food web. It has no natural predators, but of course it can be killed by their stronger prey when they are hunting, or by bears when wolves scavenge their food, and humans also like to hunt wolves.
A food web is a series of food chains. In the rain forest a food web would begin on the floor of the forest where the fertile soil grows oats, that the mice eat, that the bats eat, that the are eaten by larger animals, and some humans.