Movement Slow is a status effect applied by many items and abilities that slows movement by a percentage.
Movement speed cannot be reduced by the status effect Movement Slow below 80 hammer units (which is displayed as 2.0 m/s in game).
Stacking Movement Slow
Slows from multiple sources are multiplicative with each other.
For example, if you were slowed by Slowing Bullets for 25% and Point Blank by another 25%, your speed will be reduced by 43.6%.
Movement Slow Resist
Movement Slow Resist is applied after the final slow percentage is calculated. For example, if you had Enduring Speed with 40% Movement Slow Resist in the above example of 43.6% slow, your actual speed would be only be 26.4% slowed.