Its a form of 'aspic' (or at least it should be). Aspic can be quite a delicacy in its own right. It is traditionally there as a natural form of preservative. It tends to only be worth eating if it comes on top of classically made French pates. Often in commercial pates (regardless of cost), it is a patented recipe for a pretty generic jelly that is only there for aesthetics. It wont hurt you, but its not really part of the eating experience in this case.