It's separated and a thick something is on top of a liquidy something.
To recap: I'm trying the King Arthur starter that Tracey from Tracey's Culinary Adventures blogged about the other day. It's a super simple recipe:
2 cups warm water
1 tbs sugar
1 tbs yeast
2 cups flour
First dissolve the sugar in the water, then add the yeast. Stir in the flour. Once thoroughly mixed, cover with a towel (not plastic as this will make the flavor richer) in a warm place for 2-5 days. Each day, give it a good stir as the alcohol will have separated. It's ready when there's a nice sour aroma and the mixture no longer bubbles. Store, covered, in the fridge.