Please explain me what the differences between 'by' and 'until' are? thank you!
Paul will be away on business until Thursday. He'll be back on Thursday. (the business trip continues up to this particular time, Thursday - a period of time - 'until' says how long a situation continues)
Paul will be back by Thursday (He'll be back either before Thursday or on that day at the latest - a point of time - his return will happen by a time in the future)
(not a teacher)