Two magnets with identical dimensions and identical grade can behave in completely different ways depending on the direction in which they are magnetized. It is one of the most common details missing from a first enquiry, and one of the most expensive to get wrong.
The orientations you will meet most often
Axial: the poles are on the two flat faces, so the field runs through the thickness. This is the usual choice for discs and blocks used for holding. Diametral: the poles sit on opposite sides of the curved surface, typical for a small magnet that rotates above a sensor to report an angle. Radial: the poles are on the inner and outer surfaces of a ring or arc, common in motor rotors. Multipole: several alternating poles on one part, used in encoders and some sensing rings.
Why it cannot simply be changed later
In most high-performance sintered magnets, the powder is aligned in a magnetic field while it is pressed, so a preferred direction is built into the material itself. After sintering, the part can only be magnetized strongly along that direction. That means the orientation has to be known when the order is placed; changing it later usually means a new production lot, not just a different magnetizing step.
Put it on the drawing
State which face is north, or the number and layout of poles for a multipole part, and say whether the magnets should be delivered magnetized or not. A single clear line on the drawing prevents the rework and returns that come from assuming the wrong default.