In this chapter, I clarify the notions of mental content and of concept. I present competing views on these notions and indicate my own position. I introduce content in terms of correctness conditions and distinguish several kinds of propositions, as well as non-propositional scenario content, with which perceptual content might be identified. I relate this discussion to a wide-spread commitment in philosophy of perception to respect the subject’s perceptual perspective in ascriptions of perceptual content. Then I compare views of concepts as Fregean senses, as mental representations, and as cognitive abilities and investigate how they relate to the central idea that concepts are possessed by subjects. I suggest that our talk of concept possession and exercise is anchored in subjects’ abilities for re-identification and for general thought and in their inferential abilities. I clarify how possession and exercise of these three conceptual abilities relate.