Dry sherries have less sugar than cream sherries do. Cream sherry is made by combining dry sherry such as oloroso or amontillado with a very sweet one made from Pedro-Ximenez grapes.
Sherry is a Spanish wine. After the wine has fermented, it is classified according to the robustness of its flavor and aroma. It is then fortified with a distilled wine called destilado and aged in oak casks according to the solera system. This system adds complexity to young wines by aging them in casks that previously held older wines. The mature casks are rotated through the batches of younger sherries.
Sherry is ultimately categorized according to how it is aged and under what conditions. For example, amonitillado is covered with yeast at the beginning of the aging process to keep it from oxidizing. Later, the yeast is removed, and the sherry is exposed to air. Oloroso, on the other hand, is aged longer and allowed to oxidize throughout the aging process. Although amontillado and oloroso have about the same sugar content, oloroso has slightly more alcohol.
The Pedro-Ximenez sherry mixed with amontillado or oloroso to produce cream sherry is said to originate with a vine introduced by a German soldier. Pedro-Ximenez is the Spanish translation of that soldier's name.