It seems like you're asking about magnetic declination, which is the angle between true north (based on the Earth's rotational axis) and magnetic north (the direction a compass needle points).

Here's why it's important to understand:

* Compasses don't point directly north: The Earth's magnetic field is constantly shifting, causing the magnetic north pole to move. This means a compass doesn't always point to true north, especially when you're far from the magnetic north pole.

* Magnetic declination varies by location: The angle between true north and magnetic north changes depending on where you are on Earth. This is why it's crucial to consult declination maps or use GPS devices that factor in magnetic declination to get accurate directions.

How to find magnetic declination:

* Online maps: Several websites offer magnetic declination maps. Just search for "magnetic declination map" and enter your location.

* GPS devices: Many GPS devices automatically factor in magnetic declination, giving you accurate directions.

* Compass adjustment: Some compasses allow you to adjust for magnetic declination using a small dial.

Important note: Magnetic declination changes over time, so it's essential to check the most recent data.