What is the Pirc Defense (1... d6 or 1... g6)? On this website: http://www.dwheeler.com/chess-openings/, it says that the Pirc Defense is 1. e4 d6 or 1. e4 g6.  Which one of them is the true Pirc Defense?
1. e4 g6 could certainly transpose into a Pirc but it is not the first two standard moves. If you look at the ECO entry for B07, B08, B09 you will see the standard variations for the Pirc/Modern. I would say the link you give is wrong.

ECO B07

1. e4 d6

without 2. d4

2. d4 without 2... Nf6

2... Nf6 without 3. Nc3

3. Nc3 without 3... g6

3... g6 without 4. Nf3, 4. f4

B08

1. e4 d6 2. d4 Nf6 3. Nc3 g6 4. Nf3

B09

1. e4 d6 2. d4 Nf6 3. Nc3 g6 4. f4