English Grammar - By or Until?

http://www.engvid.com By or Until? "I will be there by 5 pm" or "until 5 pm"? What is the difference? In this English lesson, I talk about these two time prepositions, giving many different examples to highlight their meaning. By the time you take the quiz on this grammar lesson, you will know when to use by and until. You can take the quiz here: http://www.engvid.com/by-until/