AND means that both (or all for three or more) must be true.

OR means that only one of them needs to be true. Both (or all or multiple for three or more) may be true in the most elementary form of the use of OR, but they don’t have to be.

(In more advanced forms of inequalities, there is something called the exclusive OR, where exactly one must be true, not both/all/multiple. But I don’t think you need to worry about this on Khan Academy.)

By true it means that the answer for both sides must be correct right and for OR the answer might satisfy both inequalities or only one