Bipolar stepper motor
A bipolar stepping motor has an onboard driver that uses an H bridge circuit to reverse the current flow through the phases. By energising the phases while alternating the polarity, all the coils can be put to work turning the motor.
In practical terms, this means that the coil windings are better utilised in a bipolar than a standard unipolar stepping motor (which only uses 50% of the wire coils at any one time), making bipolar stepper motors more powerful and efficient to run. Although bipolar stepper motors are technically more complicated to drive, they tend to come with an inbuilt driver chip that handles the bulk of the necessary instructions and behaviours.
The trade-off is that they’re usually more expensive initially than standard unipolar versions, because unipolar stepper motors don’t require the current flow to be reversed in order to perform stepping functions - this makes their internal electronics much simpler and cheaper to produce.
Hybrid stepper motor
Hybrid stepping motors allow for yet more precision, through techniques such as half-stepping and microstepping. Microstepping is a way of increasing the fixed number of steps within a motor by programming a driver to send an alternating sine/cosine waveform to the coils. Doing this often means that stepper motors can be set up to run smoother and more accurately than in a standard setup.
Hybrid stepper motors usually have poles or teeth that are offset on two different cups around the outside of the magnet rotor. This also means steps and rotations can be more precisely controlled, as well as offering quieter operation, higher torque-to-size ratios and greater output speeds than standard stepper motors.