Universe is a term for the topology of the cells in the Life grid. In the normal universe (the usual Life arena), the grid is infinite in both directions. In a cylindrical universe, the grid is finite in one direction, and the cells at the two edges are adjacent to each other. In a toroidal universe, the grid is finite in both directions, and the cells at the top and bottom edges are adjacent, and the cells at the left and right edges are adjacent. There are several other, more obscure types of universe.
Objects found in the cylindrical and toroidal universes can also run in the normal universe if an infinite number of copies are arranged to support each other. Sometimes the objects can be supported in other ways to make a useful finite object. This is one reason that soup searches are run in alternative universes, to find such objects.