It is completely different. Before Uber, you had to call dispatch, give them your location or your closest estimate of it: dispatch would then manually try to find a car that was available and send them to you. This usually took at least 30-40m, if they arrived at all.
With Uber, I open the app, it looks at all available cars, finds the closest one available, and sends that car to my GPS location. Oh, and if that car gets stuck in traffic, it automatically picks another car and sends that over
Uber completely revolutionized taxi services and is absolutely nothing like calling dispatch on a phone.