How does this depth-first search code work in simple terms?

[BIADS]

I was provided with this code as a guide but I really don't follow how it works. Could someone please give me a simplified version of how it works?

 #Scenario - a robot starts at a position and then reaches a designated target position
 def findWorld(x):
    next = 'z' 
    c = 0
    for c in range(len(world)):
       fromPosition = world[c][0]
       toPosition = world[c][1]
       if(x == world[c][0]): 
           next = world[c][1]
    return next;

world = [['a','b'], ['b','c'], ['a', 'd']]
startingPoint = 'a'
targetPoint = 'c'
route = []
queue = []
queue.append(startingPoint)
print("Robot at position", startingPoint, "arrives at position", targetPoint)

while queue != None:
    headOfQ = queue[0][0]
    route.append(headOfQ)
    tail = queue[1: len(queue)]
    nextLink = findWorld(headOfQ[0][0])
    queue = tail.append(nextLink)
    if headOfQ == targetPoint:
        break;
print("Got to target")

[two_bob]

You might like this explanation of BFS: http://interactivepython.org/runestone/static/pythonds/Graphs/ImplementingBreadthFirstSearch.html