RNA is a fundamental biomolecule present in all living organisms. Its fate in a cell is determined by its physical interactions with various proteins. It is thus important to understand which protein binds which RNA how strongly. One major complication in predicting binding affinity of a protein to an RNA is that the constituents of the RNA molecule, the nucleotides, also interact with each other and form what is called RNA secondary structures. Since the binding energy among nucleotides and between nucleotides and a protein are comparable, there is a competition between protein binding and RNA secondary structure. In this talk I will discuss how methods from Statistical Physics are capable of quantitatively describing the interactions between RNA and proteins, the self-interactions of RNA leading to RNA secondary structure, and the competition between the two resulting in a tool that allows the calculation of the binding affinity of proteins for RNAs of arbitrary sequences.