Site-specific recombination is a form of homologous recombination targeted to a specific locus of the DNA. Using site-specific recombinases, regions of DNA with a degree of homology are aligned, and exchanged. This is used during lambda red recombination, allowing shorter sections of homology to be used in the gene of interest, to replace a gene. Likewise in CRISPR, site specific recombination lets homologous sections of just 40bp length be used.
Bacteriophages are used to insert the DNA into host chromosomes, in a similar way to prophages. A lambda phage is used during lambda red recombineering. This allows the use of integrase, and the attP (on the phage DNA) and attB (on the chromosomal DNA) sites.
Site-specific recombination is important in inserting phage DNA into a host chromosome, as it allows for shorter regions of homology while still allowing recombination to occur.