If any of the three results is false then the whole expression will be false too.

It’s like to say something like: I’m going to sing and dance in the party.

It means that you will sing and dance, both things in the party. So both expressions should be true to say that what you are saying is true

If you say: I’m going to sing or dance in the party.

This means that you could do any of the activities above, but it’s not mandatory, you could only sing but don’t dance and viceversa. So, you if you do one of the both activities then what you said is true because you said you will do one thing or the other thing, but you didn’t confirmed you will do both.

That’s the logic behind this.

If you have any other doubt then let me know!