The, can refer backwards in a conversation or text to something already mentioned.
… my sister hid a little parcel in my suitcase, so when I was unpacking the case I had a really cool surprise ...
It can also refer forwards to something which is going to be mentioned or explained.
Could you bring me the knife which you gave me?
The friend of hers who's looking after us ...
It can also refer to shared knowledge or general knowledge: Both listeners and speakers (or the writer and the reader) know what is being referred to:
But I'll try to connect from the hotel every evening.
I think Mum is hoping to see George Clooney at the bus stop.