This is a fundamental building material for use in scratch-building or customizing models.
From the Tamiya website:
This is a radio control robot model, which includes a variety of universal arm and plate parts that you can assemble into any shape you like. The set includes a 4-channel R/C transmitter & receiver set that you can use to manipulate the robot and have it perform tasks.
Use the parts in this set to construct a 3-channel radio control robot powered by 3 motors. It includes all required R/C equipment, 2 single gearboxes and a crank gearbox, plus universal arms and plates, and more. The included instruction manual shows construction of 3 exciting robot types: Twin Arm, Stag Beetle and Fork Lift! All 3 types use the same drivetrain mechanism plus the 2 wheels and single caster in the set, for forward/reverse motion, turning and pivoting. In addition to the 3 examples above, the set can be assembled in any way you like, to make your very own unique robot!
Batteries for the model (AA) and transmitter (9V) x1 are sold separately.