What do Human, Robot and Alien Resources do?

I've unlocked the part where Human Resources has turned into Robot Resources, and I know that Alien Resources come up soon, so what do they do exactly?

Human, Robot, and Alien Resources all do the same thing. They hire employees automatically. This is useful so that you don't have to click Hire Employee eight billion times just for the humans.

The only difference is what kinds of employees are currently available. That's humans until you "Secure" all of them. Then robots become available. Then you move into space and are "hiring" aliens.

In my experience, 1% is usually enough to keep up with the expansion of the potential labor force for most of the game. And there are points where 0% is fine, because there are no potential employees to hire. Although later in the game, aliens might require 4% or 5% instead.

In case, it wasn't clear, the Resources departments increase the Total Employees statistic until it reaches the Max Employees statistic. If Max Employees is increasing, then Total Employees will never quite catch up. If Max and Total are equal, then you can set Resources to 0% without other impact.