Before the Punic Wars, Rome had gradually assumed control of most of Italy. After winning the Punic Wars, Rome increased its territory into those areas Carthage had controlled. It then went after the territory that had been in Alexander the Great's empire.
On the map, the legend refers to this page and the the map of the eastern Mediterranean region. Notice the area of Hither and Further Spain. Gaul also included a hither and further region, but on this map, only the hither section, Cisalpine Gaul, is marked as Roman territory. Also note that lots of cities in Sicily are marked, but not too many elsewhere. This is a useful map not only because of the vibrant contrasting colors, but because it shows so many regions (in Italy, as elsewhere) without making the map illegible because it's so full.
