The Human Federation consists solely of members of the Human race. They are probably one of the only races to not join the United Galactic Alliance but still grow to be quite significant. The Human Federation have one of the smallest territories in the known galaxy - occupying only a dozen or so systems. Despite their size, arguably, they are the second most powerful and influential faction in the known-Galaxy.
The Human Federation is a constitutional republic, with each country on Earth getting a representative in government, as well as each colony. It is generally understood, however, that representatives from Earth generally get more respect and influence than colonial representatives. Occasionally, space stations have elected officials they may send to Earth for legislature purposes, but they do not have any voting power. At the head of the government is a president that is elected every 10 years.
The current president is Daniel Atten.
The Earth also has an emperor, Solomon Petresun. The emperor position is now merely a figurehead as far as power goes, though they do have a great deal of support from the people and they don't have much trouble developing their own ideas and pushing that agenda through the Federation legislature and made into actual law.
Compared to the UGA's fleet, the Human Federation's ships are much smaller and don't have as much firepower. However, each ship has a captain that graduated from the prestigious Human Federation Starfleet Academy, and has gained a great deal of experience, in both diplomatic, scientific and strategic affairs - all this before they are given their own command. This means that the smallest ship the Federation has to offer can prove to be a great threat to a technically larger and more powerful ship.
What the Human Federation military lacks in power, they make up for in pure skill. Even without the skill, the Federation has a vast fleet of capital starships. Most are on missions all over the galaxy, but it does not take much to call them back to protect the home front. Another great advantage that the Federation has is Warp technology which all its ships possess, allowing them to travel much faster than a UGA ship could in hyperspace.
What truly gives the Human Federation advantage and stability in the Universe is its highly advanced terraforming technology. Though various methods, the Human Federation can make a hostile world liveable in less than a decade.
The use of the Terraform Cannon is the primary method that makes this possible. The planet-based "weapon" launches a multiple independentally-targetable re-entry device that can enter high-warp speeds. It plunges into the target planet (throwing a lot of dust into the atmosphere), launching a dozen separate devices before it hits land. These devices embed themselves in various locations and begin taking in atmopshere or water and manipulating it to desired settings.
While the Terraform Cannon was designed with purely peaceful intent in mind, its value as a weapon of mass destruction is not to be underestimated. It can make a hostile environment liveable or a liveable environment very, very hostile - and it can do this rather quickly.