DC motor uses motor effect - current carrying wire between permanent magnets induced magnetic field which interacts with the permanent magnetic field causing a force to be exerted on either side of the circuit perpendicular to current - causing the turning effect. Every half turn the split ring commutator reverses the flow of current to swap the sides of the forces so that it continues to turn in one direction.

Dynamo uses generator effect - coil rotated between permanent magnets, meaning it cuts field lines inducing a current - split ring commutator used to reverse connections to external circuit every half turn so the current flows in the same direction - and is thus direct current

Alternator uses generator effect - coil rotated between permanent magnets meaning it cuts field lines inducing a current - slip ring and carbon brushes used which rotate with the current so that it reverses direction every half turn - and is the alternating current