Skills are the primary game mechanic which Rainworld characters use to interact with their world.
Skills are rated on a scale starting from 0 (no training, aptitude, or expertise at all) to 11 (the most possible).
Each skill is linked to one of the character statistics — PHYS, CON, TUF, ACU, EDU, or PPL, reflecting the general area of aptitude or achievement it falls into. The highest rank a character can have in any skill is equal to their rank in the linked statistic — although various Quirks, gear, and circumstances can improve on their raw skill.
Nobody's good at everything — characters aren't expected to have many (or any) ranks in most skills! Ideally, squads will cover most of the bases by having people specialised in different things. (And if not, you can always subcontract, or spend XP on new skills.)