A claim's scope is mostly based on simple logic. If it claims A AND B AND C AND D AND E then, as Eric said, you need to have all those to be considered inside the claim's scope.
If the claim reads (A or B) and C and (D or E) you can imagine the situation is more complicated. Sort of like searching with Boolean operators. The problem is that instead of letters A, B, C etc the claim uses words and words refer to something that might not be an object. And depending on the jurisdiction (country) you are active, the rules for interpreting claims might have their own special features.
Indeed very basic questions. Careful there, many individuals go file a PCT with a decent idea, but they try to save money by drafting themselves. Then the drafting is so poor that the damage is not repairable. And you cannot start all over again, by filing a new one (with the help of an attorney or not), because once something is published you cannot patent it anymore.