E.D.C., or the Earth Defence Command, was a human military organization created in the 21st century to defend Earth against whatever global threats that existed. It was [possibly] led by Marissa Faireborne.
The Earth orbital station observes traffic to and from the planet, with the authority to call out Autobot and/or human military assistance. The Pluto station served much the same function, its proximity to a warp gate making it a first line of defense against hostiles from non-Solar worlds. Unfortunately, even with its advanced technology, this battle platform was destroyed in a matter of moments by Galvatron and his lieutenants. It is unclear whether the Earth base would survive a similar attack. In 2006, the deep-space station near Goo was demolished by Death Crystals, even though according to Grimlock) it was built out of the strongest metal in the galaxy.
On a smaller scale, powerful technology (most likely Cybertronian) has also been incorporated in land and air vehicles. An EDC car kept up a decent fight during a high-speed road duel involving two Stunticons and Rodimus Prime. The car was armed with a roof-mounted blaster (not to mention incredible crash protection and recovery systems). Also, a similar vehicle has been seen flying despite a lack of suitable wings or the noise of conventional propulsion - just like a Transformer.
The hierarchy of the EDC is unclear, although it appears that the Autobots may be ultimately in charge. It's also unclear whether any Autobots are technically considered EDC officers. All the humans wear white uniforms with blue trim; no Autobots have been seen changing their paint jobs to fit in. :) [Ed: Yeah, that was a joke, but I'll let it slide...]