The Dimensional Anchor is the sole block added by Dimensional Anchors. It keeps a configurable number of chunks loaded, even if no players are in the area. It is analogous to the Chunk Loader and the Teleport Tether in this regard.
The Dimensional Anchor's GUI can be used to set the number of chunks loaded and the shape of the ones kept loaded. The square shape loads chunks in equal dimensions (1x1, 3x3, 5x5, 7x7, or 9x9), the "X line" shape loads chunks in a line on the X axis of the world (east and west), and the "Z line" shape loads chunks in a line on the Z axis of the world (north and south).
The GUI can also be used to set the owner of the Dimensional Anchor. The owner is the only player who can change the dimensions of the region loaded by the Dimensional Anchor. If the owner is set to the server, anyone can change the dimensions of the region.
Region Dimensions Reference
The table below demonstrates the amount of chunks loaded per-shape and per-area: