The last decade has seen lots of studies on 'animal personality' (i.e. the study of consistent between-individual behavioural differences). As timely and promising as this field is, its development has come with a diversity of research questions. As an unfortunate consequence, it now suffers from substantial confusion about what 'animal personality' is, and how relevant related research frameworks are. Here, we stress the current inconsistencies and sources of confusion pertaining to the field, and their consequences on terminology used and miscommunication between researchers. In an attempt to unravel and clarify the concepts underlying the field, we identify two distinct, but complementary, theory-driven conceptual frameworks: the intra-individual variability (IIV) approach and the life-history (LH) approach, which we believe encompass the vast majority of existing 'personality studies'. Finally, we argue in favour of theory-driven studies of consistent behavioural differences and state that the integrative statistical properties of random regression models should not override the merit of alternative conceptual frameworks. We then provide brief guidelines and warnings for a parsimonious and sound use of terminology.