Based on a screenplay by Travis Beacham, the film focuses on giant monsters named Kaiju and giant human-controlled (and humanoid-appearing) robot weapons called Jaegers. The Jaegers can vary in design, and at least one of the ones shown in a prior trailer has four arms, not two. Wikipedia's synopsis is:
When legions of monstrous creatures, known as Kaiju, start rising from the sea, a war begins that takes millions of lives and consumes humanity's resources for years on end. To combat the giant Kaiju, a special type of weapon is devised: massive robots, called Jaegers, which are controlled simultaneously by two pilots whose minds are locked in a neural bridge. But even the Jaegers prove nearly defenseless in the face of the relentless Kaiju.
On the verge of defeat, the forces defending mankind have no choice but to turn to two unlikely heroes -- a washed up former pilot (Charlie Hunnam) and an untested trainee (Rinko Kikuchi) -- who are teamed to drive a legendary but seemingly obsolete Jaeger from the past. Together, they stand as mankind’s last hope against the mounting apocalypse.
The image of the Kaiju footprint is reminiscent of that of Godzilla from the 1998 Matthew Broderick film, which is also used to show the comparative size of the beast.
The Jaegers are operated in a manner similar to some anime series and films, responding to the movements of their neural-bridged co-pilots. In other words, the pilots walk themselves in order to make a Jaeger walk. They punch to make a Jaeger punch.
The Warner Bros./Legendary picture stars Charlie Hunnam, Idris Elba, Rinko Kikuchi, Charlie Day and Ron Perlman. It opens on July 12.