In this introductory video, Professor Tim Birkhead provides an outline of the study of animal behaviour, with specific reference to Niko Tinbergen's s "four questions", by which animal behaviour is analysed. These are in terms of two "proximate" questions - how behaviour develops in an individual's life and the conditions that cause the behaviour to be exhibited, and two "ultimate" questions - how certain behaviours evolve in a species, and understanding their adaptive significance. Broad methodologies for researching these four questions are presented. The video, which is aimed primarily at students of course APS126 at The University of Sheffield, will be of benefit to students of animal behaviour on other degree courses or at A level, as well as of broader interest.