What kind of knowledge does one have when one knows what it is like to, say, fall in love, eat vegemite™, be a parent, or ride a bike? This Element addresses this question by exploring the tension between two plausible theses about this form of knowledge: (i) that to possess it one must have had the corresponding experience, and (ii) that to possess it one must know an answer to the 'what it is like' question. The Element shows how the tension between these two theses helps to explain existing debates about this form of knowledge, as well as puzzling conflicts in our attitudes towards the possibility of sharing this knowledge through testimony, or other sources like literature, theories, and simulations. The author also offers a view of 'what it is like' knowledge which can resolve both the tension between (i) and (ii), and these puzzles around testimony.