You can use your mouse to click and drag the map view around, and thus pan round the entire grid. You can zoom in or our with your mouse scroll wheel or using the slider at the bottom right of the map.
If you click on any part of the map, a small red circle appears, and below it is show the location of the circle: the region name, followed by the coordinates of the circle relative to the region. The information to the right is also updated; more on that later. 12)
At the lower left of each region square, you can see the name of the region, and then in brackets, how many avatars are currently in the region, followed by the region maturity rating.
The map itself will have icons and colored areas, depending on options you can select, in the Legend section, upper right of the window. Thus you can opt to display (or not) avatars, infohubs, land for sale, and events. You, and your home location, will always be shown (assuming the locations are visible on the map you are currently viewing).
To shift the map to your location, click the Me button. To quickly teleport home, click the Home button (note that you can also TP home quickly by pressing Shift-Ctrl-H).
The next section on the right is Find on Map. You can find various things this way:
Below the list noted above, you may type in coordinates local to the region you are looking at.
Finally, there are buttons that act on the exact location of the small red circle mentioned previously:
See this page for documentation on Firestorm 4.6.9 (42969) and earlier.