The difference between Fixed Price shipping and Calculate Shipping By Total 

Both of these calculation methods will have the same shipping rate per shipping method, but the difference is that fixed price shipping will have that same rate per shipping method for every single order regardless of the total amount orders, and calculating by total will let you have different price ranges for these rates (i.e. $0.00-$100 can have one rate for a shipping method and $100.01-$500 can have a different rate for that same shipping method).  If you only have one price range like $0-$9999999, this functions exactly the same way as fixed price shipping.