Here, I provide a guide for those new to the burgeoning field of animal welfare science as to what this comprehensive, relatively young discipline is all about. Drawing on all branches of biology, including behavioural ecology and neuroscience, the science of animal welfare asks three big questions: Are animals conscious? How can we assess good and bad welfare in animals? How can we use science to improve animal welfare in practice? I also provide guidelines for an evidence-based approach to welfare issues for policy makers and other users of animal welfare research.