Uninvolved persons are people who are not participating in the UAS operation and are not aware of its instructions and safety precautions — bystanders, passers-by, casual onlookers. A person only counts as involved if they knowingly agree to take part and know what to do.
This concept is the reference point of the whole open category: the A1 rules on overflight, the 30 m distance required in A2 and the A3 requirement to fly where no one is endangered — all of these limits are defined specifically in relation to uninvolved persons.