professional grade = ability to control all aspects of the camera...
zoom would be an aspect of the camera, used by professionals and novices... ISO, aperture, shutter speed, white balance are more "advanced" ones
do you want to just point at something and shoot a photo, similar to how your iPhone works?
If that's the case, you'll be using the automatic mode on a dSLR/point and shoot.... you get the option of playing with the more 'advanced' options if you want to down the road
Because you have no idea what you want to do and unclear about the different options are, except for "something better than an iPhone", I'd recommend you to go to a local store (eg: B&H, Adorama, Frys, Best Buy), and take a look at the different camera sizes...
"Best camera is the one you have with you" - no point in buying a bigger size if it's a hassle to carry around, and you switch back to using your iPhone 6 only (just because you have it with you). Would recommend something like a RX100 P&S or bridge camera