Until quantifier of Computation Tree Logic
$pUq$, as is, is not a well-formulated CTL (or more generally - CTL*) formula. A CTL* formula is a state formula, which starts with has a path quantifier ($A$ or $E$). 

$pUq$ is a path formula, which means it refers to a single (linear) computation. A computation satisfies $pUq$ if $p$ holds in every state until $q$ holds (and $q$ must hold at some state).

Translating to CTL, you can talk about two different formulas: $ApUq$ and $EpUq$. The former is true in a state if every path starting from this state satisfies $pUq$. The latter is true in a state if there exists such a path starting from that state.

Does that clear things up?