People standing in front of a gray building with a sign that reads' Tickets Available Here'.
The people are wanting to buy concert tickets.
Sentence 1 says tickets but does not specify what type of tickets, concert tickets, are for sale.
The tickets can be of other events than a concert
Just because people are standing in front of a building with a sign that reads 'Tickets Available Here' it does not mean they are wanting to buy concert tickets.