What is CIF (a PCB developer) and what does it do? I made a PCB (printed circuit board) for the first time, and the process included covering the board with the shape we want, exposing the board to UV light and then putting it in a developer which removes the part of the resin that was exposed to the UV radiation.

My question is, what is this developer? I think it has the commercial name of CIF (http://uk.farnell.com/cif/ar46/developer-ready-for-use-1l/dp/1783557), but what is it really? What does it do to the board and why only to the UV-exposed part?

Thanks!
Developers are usually solutions of $\ce{NaOH}$ or $\ce{KOH}$ (perhaps with some additives). Negative photoresists uses organic developers/solvents. From your description, I assume, that you use a positive photoresist. Positive photoresists are more soluble after exposition to the UV light - polymer bonds are disturbed and therefore more soluble (in areas where exposed). Please see illustration. For more detailed information look for Photoresists and Photolithography.