Your Stealth check is opposed by the Perception check of anyone who might notice you. Creatures that fail to beat your Stealth check are not aware of you and treat you as if you had total concealment. You can move up to half your normal speed and use Stealth at no penalty. When moving at a speed greater than half but less than your normal speed, you take a –5 penalty. It’s impossible to use Stealth while attacking, running, or charging.
If a character is doing nothing but hiding, there is no penalty. If the character moves up to half their base speed and are either already in stealth mode or attempt to go into stealth mode, there is no penalty. If the character moves more than half their base speed for a single action, then the character will receive a minus five to their stealth result.
An example with a normal human and no special abilities has a base speed of 30. If that human exceeds 15 feet of movement in a round when the human is attempting to hide in stealth, then that human will take a -5 penalty to that result.