The former is able to accommodate axial load in one direction, while the latter is able to accommodate it in both directions. Neither is suitable for applications that involve radial load or high-speed rotation.
Bearings whose housing washer back face is spherical (with a spherical back face or an aligning seat washer) are designed with a self-aligning capability and can accommodate the effects of inaccurate mounting.
Spherical Thrust Roller Bearings
Spherical thrust roller bearings are designed to carry high axial loads. They can also support radial load if magnitude is no more than 55% of the axial load being carried. These bearings are not suitable for high-speed rotation. Having a spherical housing washer raceway surface, these bearings are self-aligning and capable of adjusting to axial inclination. They are usually used with oil lubrication