Scalars carry a magnitude alone while vectors also need a direction, and the two standard ways of writing that direction down - quadrant bearings measured from north or south, and true bearings measured clockwise from north - with worked conversions between them.
Some quantities are fully described by a number alone. Others are useless without a direction attached — and once direction matters, everyone has to agree on how to write it down.
A scalar needs only a magnitude. A vector needs a magnitude and a direction.
In physics, force, electric current and magnetic field are all vectors. Knowing the direction of the current and the field is exactly what lets you work out the direction of the resulting force.
Direction cannot be described loosely. Any usable system needs a fixed reference, an unambiguous rule, and a precise way of measuring the angle. Two conventions are in common use, and this lesson covers both.
Sketching the compass first makes these conversions almost automatic; working from memory alone is where sign mistakes creep in.