Rogue. Lots of skills, good at melee or ranged, and the focus on dex leaves plenty of points for charisma, because I bet we'll be doing lots of persuading.
Rogue bonus damage comes from sneak attack. It's an ability that adds extra d6s to an attack. It scales with level.
And yeah, 1d8 means it rolls an 8 sided die, for a result of 1 to 8.