Stealth is all of the many ways of remaining unseen and unnoticed, as well as concealing or smuggling items on your person or elsewhere.
Attributes:
STR - Up to GM discretion and Player creativity
CON - Holding perfectly still for hours on end
DEX - Primary attribute for this skill
WIS - Aiding other people in staying quiet; moving without leaving a trace
INT - Up to GM discretion and Player creativity
CHA - Blending in with a crowd, provided your outfit/appearance doesn't stand out to much