is that the charts are up to the latest releases. Before we go into unfamiliar waters I update it at home with the latest charts, with latest corrections from NOAA. Several times this year I noticed my Garmin bluecharts in the 2-year-old GPSMAP 478 didn't show proper buoy positions (based on visual) and when I verified with the netbook below it confirmed with my visual that the Garmin chart was "off".
Coastal Explorer has an automatic update feature that syncs your charts with the latest NOAA releases and only downloads those that need updating. This works for both raster and S-57 vector.