I am always grateful for this question when it comes up. The human side of enterprise is any gathering of people for a specific purpose. That's it. It's not more complicated than that.
(And if you believe that I have a bridge in...:)
Let's give this a go and take a look at the parts. At the macro level, the enterprise is the business; at the micro level, the enterprise is a meeting, as in a leadership team meeting, a board meeting, and so on.
The purpose of the gathering is the "IT" - the driving force behind why we showed up in the first place. At the business level, the IT or ITS (plural) is to be, do or have the mission of the business; at the meeting level, the IT is to discuss objectives, goals, make decisions, and share knowledge.
The human side of the gathering is the "WE." At the business level, it is every member of the team, including the Board, and all the stakeholders, customers, suppliers, community, and so on. At the meeting level, it is every "I" that forms the WE.
In the past 100 years, we've studied the IT. We get IT. The purpose of a business, the business plan, the mission, the value statements, the process and systems, the strategy, we've got reams of research on the IT. We also have vaults of information on the WE, the organizational behavior, dynamics, and development side of enterprise. We're good to go on this end too.
It is only when we begin to discuss the "I" that forms the "WE" that we realize we've got nothing, nada. Grasping air.
Here is a clear illustration of what I mean. Phil Jackson, coach of the Chicago Bulls, said to Michael Jordan once: "There is no 'I' in team." To which Jordan famously quipped, "There is in WIN."
Turns out they were both right. Jordan was a forward guard for the Chicago Bulls; this was his role. By the time the Bulls were winning the NBA Championships, you noticed the subtle, almost graceful choreography of all the players, Scottie Pippin, Bill Cartwright, John Paxson. Jordan evolved his role into a careful complement of his teammates' roles.
Jordan perfected the "I" in time to recognize the undefeatable advantage of the perfected WE.
Now you understand the human side of enterprise - its domain is every "I" that forms the "WE." It is not the accountant, the assistant, the human resources manager, the head of operations, the IT guy, in isolation. These are roles. They have siloed organizations and individuals for decades. This separateness is ending. We're returning to cohesive, participative interaction, and our leadership styles are following in step.
Working on the human side of enterprise dives deep into how the whole person works in the business and then, with constant practice, evolves his/her excellence into a contribution of greatness.
And that is the work I do - every "I" that forms the "WE."