Topographic maps are drawn to true north (North Pole). However, a compass points to magnetic north, which is in the Hudson Bay area. The difference between true north and magnetic north is called "declination."
When true north and magnetic north are aligned (0° declination), the compass needle points to true north. If you're east or west of 0° declination, the compass is not in line with true north.
A diagram on topographic maps shows whether magnetic north is to the east or west of true north and by how many degrees.
You can correct for declination when you use a compass and a map to take a bearing, as described below.