In this chapter we present a rather wide-ranging perspective on presence as a central, characterizing feature of conscious mental life. After clarifying what we mean by presence in the first section, Sect. 3.2 discusses the implications of this for measurement. In Sect. 3.3, we consider the importance of media form for the sense of presence, before moving on in Sect. 3.4 to the relationship between presence and the sense of self considered in evolutionary terms. Section 3.5 deals specifically with attention, viewing presence as a reflection of attentional focus. Our aim is to convey the big picture about presence: what it is, what it's for, how it evolved, what it is determined by and the effects it can have.