Satisfaction is an existential concept referring to fulfilling emotional experiences. These aren't necessarily positive and pleasurable. Nor are they necessarily negative. They are simply satisfying to the brain in some way, and this satisfaction typically motivates us to perform the actions that caused them again. This likely relates to the release of hormones, but not one particular hormone -- rather, the rhythmic release of multiple hormones and personal sensitivities to them -- as well as sensory stimulation, which we now know people react to subconsciously long before that sensory information actually makes it to the conscious mind.
What experiences are satisfying vs dissatisfying can vary from one individual to the next.
For example, many people find auditory and tactile feedback to their actions to be satisfying, such as hearing the click of a keyboard or the cold of a metal pen. But others have anxieties around sounds or are easily overwhelmed by sensory input, resulting in the same experience being dissatisfying. And even for those who do appreciate auditory and tactile feedback, which types of sounds and textures are pleasant vs jarring can vary.
I like a clicky typewriter-like sound to my keyboard and am made irate by bubble-like keyboard sounds. The bubble ones sound weirdly fleshy and biological to me, and they set off some kind of primal stress instinct when I hear them in what should be a sterile environment. Meanwhile, others feels the exact opposite. The bubble ones sound safe and cozy to them because of their warm (lower) pitch and smoother sound waves, while the typewriter ones sound threatening, like the sudden beating of a stone hitting another stone beside you.
Even though these differences are really quite subtle, the moment-to-moment satisfaction experienced can have a big impact on someone's willingness to continue using a tool or technique, or to continue engaging with a story or game. They also heavily influence personal preferences in terms of style, both for the creator and the viewer.
This makes it difficult to make something that appeals to everyone equally. Even if you add lots of different settings and options in an attempt to make up for it -- such as in a videogame -- that can end up reducing the satisfaction in other ways! Maybe the interface is too cluttered now, or people need to think about too much to get started, or you're scaring off people who are indecisive and find satisfaction in something already being decided for them, or you've lost the sense of unity and intentionality that made people take the product seriously.
Satisfaction can also be experienced at other scales. For example, how satisfying the ending of a novel is depends on more than just the last word read; it's a culmination of countless other things built up throughout the course of the novel. Likewise, how satisfying a career path or life mission is depends on more than just the satisfaction of the workflow itself, as it's being influenced by things like your personal values, history, relationships, feedback, and sense of real-world impact.
There are many different systems that try to group and classify people based on what they find satisfying or where their fulfillment is derived from. These can serve as a helpful starting place to assess who your project is accommodating. Like in game design, we have the Bartle player types we can consider when designing -- players who find satisfaction in collecting, vs competing, vs exploring, vs socialzing. But ultimately, every person is an individual, and perfect matches who find every aspect of your art project satisfying are extremely rare.