In ant colony optimization, we are calculating probability based on the pheromone. Still, I have confusion how the new population is generating based on probability?
The best way to imagine ACO is as a "smart" randomization of a greedy algorithm. The "smartness", or experience of ants is stored in the pheromone. Finally, the pheromone steers the following randomized greedy algorithms in a good direction.
When you construct a solution using a greedy algorithm at each step your choice is the best option according to a local evaluation. When we use the pheromone this choice is done taking into account both the best option and the amount of pheromone.