More specifically, the issue of the legality of these prayers and prayers like these:
Videos of a number of the prayers at the heart of this case are available online. When the question of First Amendment law -- discrimination, endorsement, coercion, "respecting an establishment of religion" and all the rest -- gets too abstract, it's worthwhile to return to the actual acts being disputed.
The question is about the place of religion in the public square. The question is about the relationship between a government and a public, quasi-official religious act, and what it should be, and how to know when it is or isn't as it should be. The issue is also very concrete, though, and very specific. Did these prayers said by these ministers in this context serve, effectively, as demonstrations of government endorsements of Christianity, in violation of the Constitution's prohibition on respecting an establishment of religion?
Watch the videos for yourself.
The court's scheduled to decide the issue this term.