A photograph is technically a literal interpretation of what's in front of the lens. With all other art forms, there is a large component of the artist in the final work, due to the nature of the medium. Think about sculpture for instance. With photography this is much, much harder to do, simply because of the realist nature of the medium.
If I'm a painter, I can make a ton of choices in terms of how I portray my chosen subject matter. Brush type, paint type, specific colour palette, abstraction or not, etc. All these choices, and the way that I paint, become a rich part of the final work which is heavily imbued with my own artistic skill and vision.
With a camera, when I press the shutter, the image that was in front of the lens is transferred without any intervention on my behalf, through to the film (let's stick with film, not sensors). That's what I end up with, a literal interpretation of reality. It's much harder for me to insert some of myself, and my own vision, into that image, than if I were a painter or sculptor.
So this is the challenge and this is the one big area that separates photographers out. For good or bad, whatever, it is one of the the things that creates categories inside photography.
Many photographers find it hard to realise what their own style is. Their efforts often go into the visual side of things - how the picture will look in terms of colour or a particular editing style. But everyone else has already done that. Pretty much every different type of look you can think of has already been done. So how do you create work that has artistic value and also reflects who you are as an individual and an artist?
Coming from an analytical background of mathematics and engineering, that question was very hard for me to find any answer for, for many years! I still don't profess to have concrete answers but I have found ways of creating work that has 'me' in it - as far as I'm concerned anyway.
Really, this is the defining point for many photographers - to make the move away from the mainstream of their particular genre and start moving in their own direction. It's risky. Your following of regular viewers may not like you're new vision. This happened years ago when I switched from arty landscape and architectural LF work to portraiture. I lost virtually ALL of my followers - this was pre-Facebook, pre-Instagram - most of those followers were on Flickr and some on Tumblr and they just didn't like portraiture, period - or the fact that I wasn't using a LF camera anymore :) Silly business really. They couldn't see the continuous thread between that previous work and the new work. But there definitely was one.
At the time I made that transition between genres, I was asked to give a talk and presentation to a local Blue Mountains camera club. That was based on this topic of how to invest yourself in your work and create something of artistic value.
The guts of that presentation hinged around human emotion. For me, the key was finding topics and subjects that moved me in some way and created some level of emotion inside me. Whether it's awe, anger, amazement, rebellion whatever - there had to be a strong internal emotional response - or the work I produced would always lack depth and artistic value. The visual side of things is important but it's secondary to this. I had to have something to say with the work. Sounds simple but it took me ages to realise this - I kept looking toward the technical and visual side of things - new film, new camera, new lens, new technique blah, it's nothing, absolutely nothing. The development of the visual side will follow and develop of it's own accord if the emotional side is developed first - this is strictly right brain. And if you have a background like mine, there ain't no right brain in there.