Specialized transduction happens when only specific regions of the chromosome are transduced. This is different than generalized transduction, where any part of the chromosome can be transduced. Transduction is the transfer of genetic material from one bacterial cell to another using a bacteriophage.
This is done naturally by some phages, and laboratories have specialized techniques that encourage bacteriophages to take specific segments of genetic material from one bacterial cell and transfer them to other bacterial cells. This is how glow-in-the-dark cells are created and how bacteria can transfer antibiotic resistance between species. Joshua Lederberg and Norton Zinder discovered transduction in 1951 while testing for recombination in two strains of E. coli.