A "render hour" refers an hour of computer time it takes to generate a
visual image ("render") from raw input data such as a 3D model. The
amount of time it takes to render a given image depends on a LOT of
different factors including how complex the input data is (and how
much input data elements there are, since there can be textures,
lights, etc, in addition to the 3D model data). The "hour" varies from
computer to computer. My personal laptop might take 10 hours to render
a single image from the Bee movie, but a more powerful desktop
computer might be able to do it in just 1 hour. So just knowing that
Bee movie took 25 million hours isn't really much to go on. For a true
understanding of how long the film took to render we'd need to know
what types of computers were involved and what type of input data was
rendered.
25 million hours sounds reasonable for a movie such as Bee movie,
actually. Feature animated films like this are VERY time consuming to
render, and if they're always rendered on large collections of
computers such as the Media Grid since individual computers and even
small collections of computers aren't enough. The Media Grid has
thousands of powerful computers all connected together to render, for
example. This is known as a "render farm". - Barbara M
emphasis added
So basically they spent 200,000 hours of rendering to process the raw images into what you see as the final product. You might want to give this resource a look to start and go from there (What is Rendering?)