Kaiyodo is a Japanese company which manufactures figurines and garage kits. While the company mostly focuses on anime related characters, it does make items with other licenses like Godzilla, Gamera, Ultraman, and others.
Revoltech is a portmanteau for "Revolver Technology," in reference to the unique "Revolver Joint" articulation which all of the figures in this particular series utilize. This gives the figures a wide range of motion and stability, allowing for many dynamic and varied poses. They are a division of Kaiyodo and make figures based on the same licenses.