Rendering is making a near-photorealistic picture of a 3D design, like CGI in movies. Here's an example render of a jumping robot prototype:

In the past, we've finished a microrobot design in a 2D layout tool, extruded the 2D layers into 3D geometry and saved it in the STL 3D file format, then used the free and open source program Blender to render the STL file.