Pryor and BonJour explain Sellars better than Sellars does. See: http://www.jimpryor.net/teaching/courses/epist/notes/given.html

The basic question is over whether our beliefs are purely justified by other beliefs, or whether our (visual, auditory, etc.) perceptions themselves 'represent the world as being a certain way' (i.e., have 'propositional content') and, without being beliefs themselves, can lend some measure of support to our beliefs. Note that this is a question about representational content (intentionality) and epistemic justification, not about phenomenal content (qualia) and physicalism.