Kawase blur effect
This is a faster version of the traditional "Blur" effect. It's recommended that you use this one rather than the "Gaussian" blur effect.
Blur sets the overall strength and Quality the number of passes (higher quality is smoother but more costly). To blur more in one direction than the other, use different Pixelize X and Pixelize Y values, for example to create a horizontal motion-blur look.
Reference
All effects are listed in the effects reference page.