Nuclear pores are protein-based channels in the nuclear envelope. They regulate the movement of molecules from the nucleus to the cytoplasm, and vice versa.
Many higher eukaryotic cells have as many as 2,000 nuclear pore complexes in the nuclear membrane of each cell. This membrane or envelope keeps the DNA safe, and contains it within the nucleus.
Despite the presence of this barrier, communication still has to take place between the nucleus and the cytoplasm, so the nuclear pores serve as transportation and communication channels.