Logarithmic functions are inverses of exponential functions of the form f(x)=a^x. They can be graphed using mirroring and rotational methods. A logarithmic function is of the form f(x)=loga(x) where x>0, a>0, and a is not equal to 1. Key properties of logarithmic functions include their domain and range, extrema, asymptotes, whether they are increasing or decreasing, and end behavior.