for you example ihr = you (causal group),
so ihr braucht/you need is being said to a group of people. in english you would turn to a group of friends and ask do you need tickets? or does anyone need tickets, or do you guys need tickets, etc.
in german you could say braucht ihr tickets?
if you go back and re-read lesson 1.6 i think it'll clear things up for you in that lesson it explains this
The sie form of you is used in a global way when you are addressing
several other people, not including yourself. But beware, sie also
The Sie form of you is used when you wish to be polite or show respect
to an individual or a group. You might use it with strangers, the
elderly, teachers or authority figures. In German, addressing someone
with Sie always creates a respectful distance which can be very useful
to emphasize a point. Sie is spelled with a capital S when used in a
The du form of you is used to speak to children, friends, family
members, pets and loved ones in a casual, relaxed and familiar way.
The ihr form of you is used when you are addressing several other
people, not including yourself in a casual way, like you guys.