Computers cannot think! - however they are very good at making decisions based on logic. They can try many scenarios one after another in order to find out the best one. For example when they are trying to find a four digit number like 1,3,2,9 which could be a pin (it is not mine!). There are approx 10,000 combinations for a four digit pin - if you were to try each one on manually this would take you a long time - however a computer can do this in just a few seconds. It is called a Brute Force Attack.
Finding a route - a computer can use an Algorithm to find a route - for example they could just try all available routes until the shortest one is found - that would not be very efficient though!
A Scientist called Dijkstra found an algorithm that would do this route finding - it is called the shortest path algorithm.
Satellite navigation systems use algorithms to find the "best" route from one place to another - however they do not use Dijkstra's algorithm because it would take far too long to find the best route using that algorithm. Satellite systems use an algorithm that finds a good route but not necessarily the best route. These methods are called Heuristic. This is why sometimes your Sat Nav will take you a route that appears to be longer.
A satellite system uses Geo-stationary orbit satellites to triangulate a position on the ground using three different satellites.
The only way to find out for sure the absolute best route around Europe is to try all options - a long process. However many routes can be ruled out quickly - as soon as one route gets longer than the last best one found for that number of cities it can be discounted.
Algorithm - A step by step sequence of instructions that performs a task or solves a problem.
Route - a path from one place to another.
Dijkstra - a scientist / mathematician who discovered an algorithm to find the best route through a graph.
Sat Nav - a system used to help us find our way using satellites to find our current position on the earth.
Heuristic - a method that can find "A" solution to a problem that works but is not guaranteed to be the best one.
Brut Force Attack - try all options until the correct one is discovered.