A Pocket Dimension is a dimension inside a dimension. A Pocket Dimension is usually small and temporary. It only exists as large and for as long as its creator contributes to it. Common pocket dimensions only last for the length of a battle and are used as the battle scene for a fight. Essentially, it is a battlefield of its creator's design and manipulation. For example, take Blue Zero, a member of the Anrufe. Blue Zero's main power centers around the creation of these pocket dimensions. While the normal person must put a lot of effort into a creation of a pocket dimension, Blue Zero specializes in the activity. His common battle strategy is to create a platform floating in darkness, and trap his enemy and himself in this world on the platform. Unless Blue Zero's magic being used to allow the pocket dimension to exist is disrupted, the two are in the pocket dimension and subject to the creator's manipulation. More sophisticated and ancient spells produce permanent pocket dimensions. These dimensions usually rely on those within it and its parent dimension to keep itself powered. These dimensions usually serve particular purposes and are home to occupants. These dimensions would probably be accessed by teleportation. One such example of a pocket dimension is the one Angel Star created when she knew that the war would kill her and Jeffrey and she took her 5 year old son at that time and used a series of spells to keep him fed, content and make him more mature by the time the portal to the pocket dimension would open up for him. However there are other examples. Like Blue Zero for instance.
The exception to this rule is the Relorian race, in which each individual is born with a permanent pocket dimension, who's size and type of energy contained therein varies, tied into the Relorian's consciousness. The energy they contain depends on the sphere of Relorian magic the Relorian is born with, while its size varies depending on a large number of different factors, many of which seem unrelated.