Galaxy Map and NavComp are two different things. NavComp is used to calculate travel times between systems. You can add coordinates manually since you can only click named systems. You can also adjust the pilot skill level and ship HS speed to see their effect on travel time.
The Galaxy Map is mostly an information database. You can click on sectors to see what systems they contain, where they are etc. Systems can be clicked to list it's planets and star(s) and you will find information for each(?) one. You can even view cities that you own or belong to your faction, possibly dependent on some privs, I'm not sure.