Qualia are the subjective or qualitative properties of experiences. What it feels like, experientially, to see a red rose is different from what it feels like to see a yellow rose. [...] The qualia of these experiences are what give each of them its characteristic “feel” and also what distinguish them from one another.
Qualia have traditionally been thought to be intrinsic qualities of experience that are directly available to introspection. However, some philosophers offer theories of qualia that deny one or both of those features.
Reminds me of Socrates' distinction between right opinion and knowledge.