First, and most obvious, is the noticeable absence of finger grooves on the grip.
The second change is a flared magwell and large front cutout. This is to facilitate quicker loading and reloading.
The magazines themselves have a distinct difference. While they are interchangeable with previous generation right-handed mags, the new 15-round standard magazine has an orange follower.
The fourth major change is the ambidextrous slide stop. The Gen 5 has a slide stop on the left and right side of the slide. Side note: Five years ago, I taught my Dad, who is left-handed, how to shoot with a Glock and I wish the ambi stop had been around then!
Another major difference is the nDLC finish. This protectant on the slide is specific to new Glocks and they claim it is more durable than previous models, but of course that's only something that can be tested over time.
The new models also feature a beveled muzzle which is to prevent potential problems when quickly removing the gun from the holster.
This G19 Gen 5 had Ameriglo sights—although they offer three dot night sights and plastic OEM sights as well.
The gun has a Marksman barrel, which uses a more traditional hexagonal rifling instead of Glock's known polygonal rifling.
The firing pin has been squared along with a squared ledge and rampings
The trigger system is also changed. One element involves a throwback to older Generation 1 and 2 Glocks. The original firearms only had one pin in the mechanism. A locking block pin was added for later generations featuring heavier calibers. But the Gen 5 has gone back to a one pin system, meaning heavier calibers are likely not an option for the Gen 5 in this configuration.