Each of these methods of genetic exchange can introduce sequences of DNA that share little homology with the remaining DNA of the recipient cell. If there are homologous sequences shared between the donor DNA and the recipient chromosome, the donor sequences can be stably incorporated into the recipient chromosome by genetic recombination. If the homologous sequences flank sequences that are absent in the recipient, the recipient may acquire an insertion from another strain of unrelated bacteria. Such insertions can be small or quite large. Large insertions that have been acquired from another bacterium (often inferred from differences in GC content or codon usage) and are absent from related strains of bacteria are called "islands".
This of course differs from normal inheritance since not the entire genome of the bacteria gets copied but only parts. Horizontal gen transfer is of great importance to treating infections. If certain bacteria are immune to say antibiotics. Then they can pass this trait by means of horizontal gen transfer. This is why when take antibiotics its of great importance to finish the given regime. You want to make sure that all bacteria are dead and none of them can develop a Resistance. Because of demands of food industry and other factors where loosing this battle however. More and more super-bugs are appearing over the world. Such as MRSA bacteria.
Now for evolution well that you can answer for yourselff.