Yep, the poster is a composite from a number of sources which was put together in Photoshop. In your Photoshop help files reside reasonably good descriptions of the Blend Modes.
A more comprehensive description and example of each is found here...
http://www.arraich.com/ref/tool_blend_modes.htm
This is the index page with a brief description of terms and the modes. Each name is a link to an example page. I'd also suggest you open an image in Photoshop, make a second layer of some smaller item, even a square of color and practice by changing the blend modes to see what happens as you read the descriptions.