Puzzle of the week #336

Level: 
2-Knight
Chess Diagram: 

[Event "Puzzle #336"][Date "2018.02.18"][Result "1-0"][SetUp "1"][FEN "r4rk1/1b2bppp/2pp1n2/q2Pp3/4P3/2N1RN1P/B1P2PP1/R2Q2K1 w - - 0 1"]

We have an equal position with white being strong in the center, while black is pinning Ba2 and attacking Nc3. This forces both white Rooks to defend. Your tasks:
a) What part of the game are we in and why?
b) How is the center right now?
c) Can you find the nice trick white used to win material? What is its name?

Total available points for this puzzle is 20. The answers will be published next time together with puzzle #337.

Puzzle #335 solution:
FM Marius Ceteras, 2007. This week's best answers are by the top scorers:
a.) The bishop is better since the position is open (there are no pawns in the center) and the bishop can control long diagonals. In closed positions, the knight is better because it can jump around; this is not the case here
b.) The white king is safer, even though the rook is cutting off the e-file, black does not have any pieces attacking the white king except for the rook. There are pawns protecting the white king and black does not have any pawns to protect him

[Event "Puzzle #335"][Date "2018.02.12"][Result "1-0"][SetUp "1"][FEN "8/2k3n1/8/4rp2/6p1/B5P1/5P2/R4K2 w - - 0 1"]1. Bb2 Re7 2. Ra7+ Kd6 (2...Kd8 3. Bf6 Ke8 4. Rxe7+) 3. Ba3+ Ke6 4. Rxe7+

Correct solutions:
Matthew, Lyvia - 20 points
Coby, Eric, Megbai, Walter, Joey, Blake - 18 points
Aiden, Zhengyu, Itamar, Lucas - 17 points
Glyn - 15 points
Brian - 12 points

Standings:
Matthew - 90 points
Eric - 85 points
Lyvia - 80 points
Coby - 69 points
Joey - 61 points
Aiden, Zhengyu - 60 points
Mengbai - 59 points
Glyn - 55 points
Brian - 50 points
Itamar - 45 points
Jacey, Lucas - 41 points
Blake - 39 points
Walter - 28 points
Darius - 8 points
Chris - 3 points

Comment: 

Discovered attack