meaning of phrase 'supposed to'

how to use ‘supposed to’

You were supposed to be here at 8 o’clock.

You were supposed to wear a suit for the wedding.

You were supposed to be my friend.

You are supposed to start every new sentence with a capital letter.

And end it with a full stop.

Or a question mark perhaps?

I too thought of that, but was it a direct question Andrea ?

Well, it has to be a question. Otherwise it would sound like the headline of an explanatory article on the subject.